The state TV said on Wednesday that regime troops "restored security and peace" after successfully dismantling the "terrorist networks" operating in the town over the last few days.
Lebanon's Al-Mayadeen TV, which has reporters embedded with Syrian troops, was reporting live from the town, showing images of damaged buildings. The reporter said there was no sign of fighting.
One Hezbollah fighter told Reuters, "We did a sudden surprise attack in the early hours and entered the town, they escaped," he said.
Syrian rebels said in a statement that they had withdrawn overnight Wednesday from Qusair after an onslaught by the Syrian army and Hezbollah fighters killed hundreds of people.
"In face of this huge arsenal and lack supplies and the blatant intervention of Hezbollah... tens of fighters stayed behind and ensured the withdrawal of their comrades along with the civilians," said the statement, which was sent to Reuters.
For Assad, Qusair is a crucial link between Damascus and loyalist strongholds on the Mediterranean coast. The Recapturing of the town, in central Homs province, could sever connections between rebel-held areas in the north and south of Syria.
Syrian government offensives in recent weeks are an apparent attempt to strengthen Assad's negotiating position before peace talks next month sponsored by the United States and Russia.