Kailer Yamamoto also scored, and Sebastian Cossa made 15 saves for the Mammoth (7-3-0), who have won four of their past five games.
Erik Karlsson and Rickard Rakell each had a goal and an assist, and Bryan Rust had two assists for the Penguins (3-6-1), who have lost four in a row and seven of their past eight (1-6-1). Arturs Silovs made 24 saves.
Egor Chinakhov cut the Utah lead to 5-3 at 2:55 of the third period. He caught a pass in stride from Andrei Kuzmenko, powered past the defense and snuck a shot five-hole.
Declan Carlile brought the Penguins to within 5-4 at 14:55, jumping on a rebound from Rakell's point shot and burying it from the left face-off circle.
Cossa denied Ben Kindel's point-blank chance with a sprawling left pad save in the dying seconds of the third to preserve the win.
Karlsson opened the scoring with a power-play goal at 1:11 of the first period, firing a puck from the point that went off the left skate of Mammoth defenseman MacKenzie Weegar and past Cossa to give the Penguins a 1-0 lead.
Keller tied it 1-1 at 6:00. Lawson Crouse fed a no-look pass from the left corner into the slot, where Keller pounced on it and backhanded the puck over Silovs' glove.
Stenlund scored at 10:10, flipping a rebound over Silovs off a shot from Mikhail Sergachev to give the Mammoth a 2-1 lead.
Rakell evened the score 2-2 with a power-play goal at 7:01 of the second period. He collected a pass from Rust at the left of the net and swung around to tuck the puck past Cossa's left skate.
Schmidt regained the lead for the Mammoth 3-2 at 11:44 when he blasted a shot from the blue line past a screened Silovs.
Kailer Yamamoto scored at 14:40, tapping in a pass from Schmidt to extend the lead to 4-2.
Schmaltz extended it to 5-2 with a power-play goal at 1:36 of the third period, collecting his own rebound in front and tucking the puck around Silovs' right skate.
