The group, which is fighting against the government of Syrian President Bashar al-Assad, posted the statement on its Twitter account on Thursday.
The bombing was carried out at Hermel’s main square in front of a state building, killing at least three people, injuring 30 others.
The town is located 10 kilometers from the Syrian border. It has a pro-Hezbollah majority population and has witnessed numerous rocket attacks by foreign-backed militants in Syria.
The al-Nusra Front announced its presence in Lebanon on December 17, 2013, when it takes responsibility for a rocket attack on Hermel.
The attack came about two weeks after a powerful car bomb blast hit the Haret Hreik neighborhood in the Lebanese capital, Beirut, killing several people and injuring dozens of others.
The al-Qaeda-linked Islamic State of Iraq and the Levant (ISIL) claimed responsibility for the attack two days later.
Beirut has been repeatedly targeted by similar terrorist attacks in recent months, which have left a large number of casualties.
On December 27, 2013, several people, including former Finance Minister Mohamad Shatah, were killed in a car bomb attack near Lebanon’s parliament in Beirut.