Andrew Messmer objected to Keith Harris hanging around his girlfriend and trying to smoke crack cocaine, police said.
But when he complained to Harris, Harris slashed Messmer on both his forearms with a box cutter, according to Ferry-Fillmore District police.
Harris, 53, of the first block of Mills Street, was charged with assault following the attack shortly before 6 p.m. Tuesday.
Officer Michael J. Norwood said he apprehended Harris at the intersection of Broadway and Gibson Street and returned him to the scene of the incident on the first block of Woltz Avenue where he was identified as the attacker.
Messmer, 58, was taken by Rural/Metro Medical Services ambulance to Erie County Medical Center, where he was treated and later released.