President Obama and his administration had delayed making such a determination even though other countries had accused the regime of Syrian President Bashar al Assad of using sarin gas on rebel forces.
The use of chemical weapons has long been considered a "red line" by the President Obama to take more forceful action against the Syrian regime.
"Following a deliberative review, our intelligence community assesses that the Assad regime has used chemical weapons, including the nerve agent sarin, on a small scale against the opposition multiple times in the last year," according to Deputy National Security Advisor Ben Rhodes.
Traces of chemical weapons were detected inside Syria months ago, but President Obama had insisted on a thorough investigation by the intelligence community to determine who had used them.
It remains to be seen what any new action will consist of. But some options include more direct aid to rebel forces who are bent on topping the Assad regime, instituting a no-fly zone or even committing U.S. forces to Syria.
The determination that Assad used chemical weapons might not lead to immediate U.S. intervention.
"The Obama administration will make decisions going forward 'on our own timeline,'" Rhodes told reporters.
Lawmakers from both parties had called on the Obama administration to do more.
Sen. John McCain, who has been vocal on the need for more U.S. action against the Assad regime, praised the finding by the government and pressured President Obama to offer "lethal assistance" to rebels forces.
"But providing arms alone is not sufficient," said McCain in a joint statement with South Carolina Republican Lindsey Graham.
"That alone is not enough to change the military balance of power on the ground against Assad. The President must rally an international coalition to take military actions to degrade Assad's ability to use airpower and ballistic missiles and to move and resupply his forces around the battlefield by air. This can be done, as we have said many times, using stand-off weapons such as cruise missiles."
"We cannot afford to delay any longer," they added. "Assad is on the offensive with every weapon in his arsenal and with the complete support of his foreign allies. We must take more decisive actions now to turn the tide of the conflict in Syria."
Sen. Saxby Chambliss, who sits ont he Senate Intelligence Committee, said Thursday night he would support an American military operation against Syria.
"I have said for the last several weeks that doing nothing continue, continue to do nothing is not an option," said Chambliss, "We know now that almost 100,000 or maybe an excess of 100,000 people have been killed inside Syria – and the United States has sat by and watched that happen. We now know that the president said a red line was the use of chemical weapon, we know now that chemical weapons have been used for almost a year by the Syrian regime. We've done nothing. I think it's time that we act in a very serious way, if a no fly zone is what they've decided to do – I am sure our military is taking the right preparations for carrying out a successful operation. And I will support that."