Hartman has goals in four straight games, including two in a 5-2 victory against the Vancouver Canucks to help Minnesota clinch a Stanley Cup Playoff berth on Thursday.
Jonas Brodin and Jake Middleton also scored for the Wild (43-21-12), who have won three of their past four games.
Drake Batherson scored for the Senators (39-27-10), who have lost four of five (1-3-1) and were unable to pad their lead for the second wild card in the Eastern Conference. Linus Ullmark made 19 saves.
Jake Sanderson played for the first time since March 7 after Ottawa’s top defenseman sustained an upper-body injury on March 7.
Brodin gave Minnesota a 1-0 lead at 9:45 of the first period when his shot from the top of the left face-off circle rebounded off Ullmark and then deflected off the skate of defenseman Nikolas Matinpalo.
Hartman made it 2-0 at 15:35, capitalizing on a turnover by Jordan Spence at the offensive blue line that led to a 2-on-0 the other way. Hartman finished a feed from Mats Zuccarello off the rush.
He then gave the Wild a 3-0 lead at 15:31 of the second period, scoring on a wrist shot after another pass from Zuccarello.
Middleton made it 4-0 at 12:46 of the third period. He skated in from the blue line into the left circle and ripped a wrist shot past Ullmark. It was Middleton’s second goal of the season and first since Jan. 3.
Batherson ended Wallstedt’s shutout at 16:43. He was struck by Lassi Thomson’s shot from the blue line but managed to put the puck past Wallstedt while falling for the 4-1 final.
