"RAF Tornadoes have just returned from their first offensive operation over Syria and have conducted strikes," a spokesman for Britain's Ministry of Defense (MOD) said early Thursday.
The four jets took off from Akrotiri air base in Cyprus, targeting an oil field in Eastern Syria, the MOD told CNN.
More details on the operation are expected from the ministry later today.
Lawmakers voted 397 in favor of action and 223 against, following a 10-hour debate.
After the November 13 terror attacks in Paris, France asked the U.S.-led coalition to bump up the military offensive against ISIS.
Now that Britain has decided to expand airstrikes that it previously conducted only in Iraq, the spotlight is on the German Parliament, which also is expected to approve greater military commitment against the terror group.
The German plan would activate 1,200 troops in anti-ISIS efforts, but in a support role -- not direct combat.
U.S. President Barack Obama welcomed the British move and said the coalition would work "to integrate them into our coalition air tasking orders as quickly as possible."
Prime Minister David Cameron kicked off the debate by saying that ISIS is a threat to the British people, proved in part through the beheadings of UK hostages in the Middle East and other atrocities.
"This is not about whether we want to fight terrorism. It's about how best we do that," Cameron said.
He said the UK faces "'a fundamental threat to our security" and posed the question, "Do we work with our allies to degrade and destruct this threat ... or do we sit back and wait for them to attack us?"
"This is the right thing to do to keep Britain safe, to deal with this evil organization and as part of a process to bring peace and stability to Syria," Foreign Secretary Philip Hammond told CNN.
Hammond said the military campaign will have two stages: airstrikes to degrade ISIS capabilities and an eventual ground assault.
The airstrikes can begin "pretty much straight away" after the vote passes, he said.
In his rebuttal to Cameron, Opposition leader Jeremy Corbyn called the Syria decision "one with potentially far-reaching consequences for us all, here in Britain, people in Syria and those in Middle East."
Corbyn called for Cameron to explain "how British bombing in Syria will contribute to a comprehensive, negotiated, political settlement of the Syrian war."
After the vote, Corbyn tweeted that Cameron pushed for the Parliament vote after he saw opposition in the country was growing. Corbyn said a diplomatic settlement on Syria should be the goal.
Britain's Parliament voted in 2013 against UK military action in Syria. Lawmakers in the House of Commons rebuffed Cameron's call for a strong response to allegations the Syrian government had used chemical weapons in the civil war. Parliamentary authorization has only been given for UK military action in neighboring Iraq as part of the international coalition against ISIS.
German legislators on Wednesday were debating on an expanded commitment, deploying high-tech intelligence jets over Syria and northern Iraq to help other countries' forces pinpoint targets.
The Cabinet, representing a country known for its reluctance since World War II to engage in military adventures abroad, approved the military support mission against ISIS in Syria this week. Lawmakers must approve it, too, before it takes effect.
The measure reportedly has overwhelming political support, with only two smaller parties objecting. The vote is widely seen as a rubber stamping of Chancellor Angela Merkel's recent commitment to France's Hollande.
In addition to sending troops and equipment in a support capacity against ISIS in Syria, Germany would strengthen its training mission in northern Iraq, according to German public media news site Deutsche Welle.
Germany has not committed to airstrikes, and its post-World War II constitution hinders it in participating in battle on foreign soil.
U.S. 'special operators'
The United States has already been pummeling ISIS' de facto capital of Raqqa, Syria. On Tuesday, Defense Secretary Ash Carter announced the United States will send in a special targeting force
to carry out raids against ISIS in Iraq.
"In full coordination with the government of Iraq, we're deploying a specialized expeditionary targeting force to assist Iraqi and Kurdish Peshmerga forces and to put even more pressure on ISIL," Carter said before the House Armed Services Committee, using another name for ISIS.
"These special operators will over time be able to conduct raids, free hostages, gather intelligence and capture ISIL leaders."
The force is in addition to the "less than 50" Special Operations Forces that Obama authorized in October to aid in the fight against ISIS in Syria.