Vincent Lecavalier and Carlo Colaiacovo also lit the lamp for the Flyers, who have won five straight in the Steel City and improved to 11-1-1 all-time during the regular season at the arena which replaced the Igloo.
The win snapped a nine-game road losing streak for the Orange and Black.
It also gave them their first victory away from home since February 15 in Buffalo. No team has lost 10 in a row on the road since Dec. 27, 1991 through Feb. 4, 1992 (0-8-2) when Bill Dineen was in the early stages of taking over for Paul Holmgren as head coach.
Sidney Crosby supplied the lone offense for the Penguins, who have lost seven of their last 10. Marc-Andre Fleury allowed all four goals on 31 shots in another home setback to their cross-state rivals.
Schenn tapped in a Jakub Voracek slap pass in front on the tail end of a carryover power play for a key insurance goal and a 3-1 Philly lead just 49 seconds into the third period.
Colaiacovo then followed up a Michael Raffl miss and converted from the left side at 5:34 to make it a three-goal spread.
Mason kept the injury and penalty-prone Penguins off the board for the remainder, picking up just his second road win of the year.
Their current seven-game win streak over the perennial hot pick to win the division and advance deep into the Eastern Conference playoffs matched a similar roll from Feb. 18-Dec. 22, 1985, and trails only a nine-game run from 2/2/80 to10/29/81 and the all-time record of 11 consecutive victories over the pre-Lemieux club from 12/12/82 through 3/28/84.
Things looked good early on for the struggling hosts, as Crosby chipped in a Patric Hornqvist rebound at the right post just 3:29 into the contest.
However, the game reverted back to form for the visitors. Lecavalier won a right-circle draw and then scored his second goal of calendar year 2015 off a Pierre-Edouard Bellemare rebound at 17:14.
Schenn put the Flyers on top to stay when he followed up a broken rush and, thanks to some lax defensive coverage, scored on a wrister from the slot for a 2-1 game at 12:43.
Notes: Philadelphia's record stands at 13-2-1 in 16 total appearances at Pittsburgh's new hockey venue ... Crosby's marker was his 300th career goal, coming in his 622nd game ... The Pens captain joined Mario Lemieux, Jaromir Jagr, Rick Kehoe and Jean Pronovost to score as many with the franchise ... Colaiacovo netted his first goal since March 9, 2014 for the Blues ... Schenn posted his fourth multi-score effort of the season and first since March 14 against Detroit.