The following is a timeline of the Syrian Civil War from August to December 2015. Information about aggregated casualty counts is found at Casualties of the Syrian Civil War.

August 2015

11 August Rebels begin their push into the Alawite heartland by capturing much of the Sahl al-Ghab plain in northwestern Syria.

16 August

According to the Syrian Observatory for Human Rights, four separate missiles were fired at Douma by SAAF fighters, which struck the main market in the town during rush hour, killing 96 people.

22 August At least 50 people - mainly women and children - are killed when the Assad regime targeted the Douma town in an opposition-held suburb of Damascus with barrel bombs. A number of buildings were destroyed by the attacks, while another 100 are injured.. Retrieved 2015-09-20.

30 August ISIS fighters launch an assault on Qadam and Asali in the southern outskirts of Damascus from their base in Al-Hajar al-Aswad, clashing with Jaysh al-Islam fighters in Qadam and those of Ajnad al-Sham in Asali.Islamic State battles Syrian rebel forces in Damascus. Retrieved 2015-09-02.

September 2015

1 September Levant Front clandestine security conducted an undercover raid into an area under ISIS control in the northern Aleppo countryside, killing three foreign fighters of ISIS.Syrian rebels say kill foreign ISIS fighters in undercover strike. Retrieved 2015-09-02.

2 September Digital reports surface on the web of a possible Russian Air Force bombing campaign in Syria, mostly targeting ISIS & other Islamist objectives.PHOTOS ALLEGEDLY TAKEN OVER IDLIB SEEM TO PROVE RUSSIAN MIGS, SUKHOIS AND DRONES ARE CURRENTLY OPERATING AGAINST ISIS IN SYRIA. Retrieved 2015-09-04.Russian jets in Syrian skies. Retrieved 2015-09-04.

4 September Fierce clashes took place in the vicinity of Marea town north of Aleppo, where Levant Front rebel soldiers killed seven ISIS militants and took 11 others as hostages, beside destroying three ISIS vehicles. The Shamiya Front also seized heavy machine guns from ISIS militants, as dozens withdrew from the area after "heavy losses".Seven ISIS militants killed in renewed clashes with Syrian rebels near Aleppo . Retrieved 2015-09-04.

Other rebel factions attacked ISIS-held villages of Harbal, Sandaf, Kafrah and Harjal in the northern countryside of Aleppo. It was not clear whether the attacks caused any casualties in the ranks of ISIS.

5 September Anti-government violence erupted in the town of Sweida, a stronghold of the Druze minority sect, following the killing of Druze leader Sheikh Wahid Al-Balous, a prominent cleric in rare explosions the previous day that claimed the lives of at least 25 others. Rioters holding the government responsible for the cleric's death destroyed the statue of late President Hafez al-Assad and besieged security offices.Violent protests hit Syria's Sweida city. Retrieved 2015-09-06.

6 September Israeli Prime Minister Benjamin Netanyahu rejects notion of accepting Syrian refugees."One country that won't be taking Syrian refugees: Israel", Batsheva Sobelman. Los Angeles Times. 6 September 2015. Accessed 5 May 2017

11 September A Syrian military source informs of Russian troops presence in Syria.

Jaysh al-Islam shelled and stormed Adra Prison, taking control of two buildings.

15 September The Levant Front shoots down an M6 warplane for the pro-Assad air force near the Nairab military airport in Aleppo province, and seizes control of major parts of Hamdaniyah district after fierce clashes with pro-Assad militias, killing at least fifteen regime soldiers. The Front also bombs pro-Assad security headquarters in Salahaddin neighborhood. The regime forces responded with dropping more than six barrel bombs on the rebel-held neighborhoods of Dahiya and Shekhan in Aleppo, killing more than ten civilians.Syrian rebels shot down warplane, advance against pro-Assad forces in Aleppo. Ara News. Retrieved 2015-09-17.

16 September At least 15 civilians - six children and nine women - are killed and dozens injured after pro-Assad warplanes launch some four rockets targeting residential buildings in rebel-held al-Maadi neighborhood in Aleppo city in the evening, with more than 25 injured.Pro-Assad forces commit new massacre in Aleppo. Ara News. Retrieved 2015-09-17.

17 September A short video is released purporting to show Free Syria Army (FSA) soldiers in Idlib installing sensor wires on a new DIY missile defense system for areas under their control to provide some protection to the civilians and planning to continue the project in other cities.Northern Syrian rebels claim to build their own air defense system. Ara News. Retrieved 2015-09-18.

Government helicopters drop barrel bombs that struck a busy market place, that is packed with shoppers and people buying necessities for children who go back to school this week, in the FSA-held Bosra, killing between 17 and 24 people and many others wounded, with many of them in critical condition.Syria carries out rare attacks on ISIS capital. Retrieved 2015-09-18.

At least 47 people were killed in air raids by Syrian government forces in rebel-held areas of the northern city of Aleppo.

Syrian warplanes carried out a wave of airstrikes in the Islamic State-held city of Raqqa.

18 September United States Defense Secretary Ashton B. Carter opened a dialogue regarding Syria with his Russian counterpart, Sergei K. Shoigu, aimed at making sure that American and Russian forces avoid running into each other. U.S. Begins Military Talks With Russia on Syria. The New York Times. Retrieved 2015-09-27.

The Islam Army posts a video showing its members firing multiple rockets at the Latakia International Airport on the coast used by Russian troops, and warns the Russians that they will not enjoy peace in Syria.Syrian rebel group claims it attacked base used by Russians . Timesunion. Retrieved 2015-09-19.

21 September Pro-Assad forces targeted al-Shaar neighborhood in eastern Aleppo city with surface-to-surface missiles, hitting a crowded public market, killing more than 30 civilians and dozens wounded.Pro-Assad forces target Aleppo public market with missiles, dozens killed. Ara News. Retrieved 2015-09-24.

22 September Syrian army recaptures villages in Hama suburbs.Syrian army recaptures villages in the north . Yahoo News. Retrieved 2015-09-23.

24 September

More than 2 months after the siege began, the UN announced that an agreement between the warring parties had finally been reached after repeated mediation efforts. Per the agreement, the remaining entrenched rebels were able to withdraw from Syrian government besieged Al-Zabadani and lease control of the town to the Syrian government while surrendering all weapons, save for light handguns, and withdrawing to the Idlib Province. Conversely, civilians (approximately 10,000 people) still remaining inside the rebel-besieged Shi'ite villages of Al-Fu'ah and Kafriya are to be evacuated. Evacuation of wounded from both sides was expected to begin as early as 25 September. An additional stipulation denotes the release of 500 rebel captives from Syrian government-held prisons. The agreement would be overseen by the United Nations office in Damascus. However, SOHR reported on 26 September that a rebel fighter had been killed in a firefight with the NDF near the villages of Al-Fou’aa and Kafraya.

Two days later the first bus transport evacuating the rebel combatants to Idlib began leaving Al-Zabadani.

The ceasefire was still in effect despite a couple of violations on 27 September.

26 September The U.S. military admitted that US-trained Syrian rebels has handed over their vehicles and ammunition to fighters linked to al-Qaeda, apparently to gain safe passage.Syria crisis: US-trained rebels give equipment to al-Qaeda affiliate. BBC. Retrieved 2015-09-27.

27 September Its reported that the British Prime Minister David Cameron did not rule out that Assad could be part of a transition, but "what he is very clear about is that Assad cannot be part of Syria's future in the long run."Cameron: Assad could stay for the short-term. Al-Arabiyah News. Retrieved 2015-09-27.

France starts launching its first air strikes in Syria targeting ISIS training camps.France launches air strikes against Islamic State in Syria. Reuters. Retrieved 2015-09-27.

Russian President Vladimir Putin branded U.S. support for rebel forces in Syria as illegal under the UN charter and ineffective, saying U.S.-trained rebels were leaving to join Islamic State with weapons supplied by Washington, according to the American military's own reports.U.S. support for Syria rebels illegal: Putin. Reuters. Retrieved 2015-09-27.

29 September Digital Reports informs that the Pentagon has suspended the "train and equip" program for Syrian Rebels also known as New Syrian Forces (NSF).Report: Pentagon Suspends Syrian Rebel Training Program. news.antiwar.com Retrieved 2015-09-29.

30 September Russia starts bombing Syria.

October 2015

4 October Egyptian President Abdel Fattah el-Sisi expressed its support to the Russian military intervention in the Syrian Civil War.Egypt supports Russia’s military moves in Syria. english.alarabiyah.net Retrieved 2015-10-04.

7 October 4th Hama Offensive begins with Iranian and Russian support.

The FSA repels an offensive mounted by Assad forces in the countryside near Hama, destroying 10 government tanks – despite coming under repeated Russian air assault.Syria Rebels Repel Ground Assault, Call for US Help. VOA. Retrieved 2015-10-09.

8 October FSA rebels claim to have downed two regime helicopters that were mounting a coordinated air assault with Russian warplanes on the village of al-Mugheer. Meanwhile, the Syrian Army captures 40 km of territory in northern Hama

10 October On 10 October, it was reported that the Syrian Army captured the strategically important villages of Atshan and Om Hartein and that it was pushing onwards to capture Khan Shaykhun in southern Idlib province. A number of government tanks and APC's were destroyed during the clashes. Hezbollah senior leader Hassan Hussein al-Haj was killed that day.

14 October A U.S. official told Fox News that Russian Airstrikes have killed 150 CIA trained rebels in "deliberately targeting" during its Intervention in Syria.

20 October Military officials of Russia and the U.S. signed a "memorandum of understanding" to avoid clashes in air over Syria.

The new elected Prime Minister of Canada, Justin Trudeau announced that his nation will no longer provide jets fighters for the fight against ISIS.

Former U.S. President Jimmy Carter announced that he provided maps of ISIS positions in Syria to the Russian embassy in Washington.

Russian warplanes struck a field hospital in the town of Sarmin killing 13 people, including two medical staff. A physiotherapist, Hassan Taj al-Din, and a hospital guard from the clinic, which was run by the Syrian-American Medical Society (SAMS), were killed in the attack. Taj al-Din leaves behind his four-months pregnant wife.Russia air strikes target Syria field hospital killing two medical staff and 10 civilians. Retrieved 20150-11-07.

28 October Regime forces conducted airstrikes that dropped as many as 12 barrel bombs on the town of Darayya in multiple raids, killing at least three people including a woman and her son.Syrian regime barrel bomb falls metres from man filming attack in Daraya. Retrieved 2015-11-07.

29 October The Syrian Observatory of Human Rights reported that according to a defected ISIS leading figure from Syrian descent, over 200 ISIS fighters from Chechnya and central Asian nationalities were executed for trying to defect from IS to join Jabhat al-Nusra.

31 October IS captures Mheen and Hawwarin, west of Al-Qaryateyn city.

November 2015

2 November Jaysh al-Islam a major rebel group near the capital Damascus, displayed caged civilian captives used as 'human shields'.

5 November