Drew Stafford and Steve Ott scored for the Sabres.
Sabres backup goalie Jhonas Enroth stopped 25 shots, dropping to 1-11-5 this season and 0-9-4 in his past 13 starts.
The Sabres came up empty in extending their home skid to 0-4-3 — the team's longest since opening the season 0-8-1 in Buffalo.
Buffalo gave up the first goal 32 seconds in, was unable to hold a 2-1 lead and then gave away the game while it was on the power play.
With Ryan Nugent-Hopkins off for hooking, the Sabres turned the puck over inside the Oilers blue line. Edmonton forward Boyd Gordon got the puck and threaded a pass through the middle to hit Hendricks, who had sneaked in behind Buffalo's defenders. Breaking in alone, Hendricks backed Enroth into the crease and lifted a shot inside the left post.
"Great pass," Hendricks said. "I give him a lot of credit. It was a pretty play. I'm sure I would've just dumped it in."
Hendricks is a defensive-minded forward who was acquired by the Oilers in a trade with Nashville two weeks ago.
Oilers coach Dallas Eakins is impressed with what Hendricks has provided on and off the ice.
"He's preaching all the stuff that we need here," Eakins said. "He's been a good penalty-killer for us, but definitely a guy that's very vocal. I think a lot of our guys need to be listening to that because he certainly knows what he's talking about."
Hendricks was happy to contribute with his second goal in nine games for Edmonton.
"Your bread and butter is the defensive style of game, so any time you get an opportunity to add to the stat sheet, it's a good feeling," Hendricks said.