A knifepoint robbery aboard the 2 train went awry when one victim stole the robber’s knife and used it against him, police sources say.

The brawl broke out aboard a northbound train near the Bronx Park East station just before 7 p.m. Thursday when two 18-year-old men were approached by a group of eight people.

Sources close to the investigation tell News 12 that one robber, a 17-year-old boy, stole one man's cellphones before a fight broke out, and the 17-year-old slashed the man in the face and arm.

The man fought back and obtained the teen’s knife, which he used to stab him, sources say.

Meanwhile, the second victim was punched in the face by another in the group. His cellphone was also snatched.

Sources say the group of robbers, including the teen, exited the train and ran away before the teen called 911 to report he had been stabbed.

EMS took the teen to the hospital and placed him in police custody. He is expected to recover.

The 18-year-old slashing victim was also hospitalized and is expected to be OK.

No official charges have been filed as of Friday evening.