The win extended Calgary's streak to five games without a regulation-time loss to begin a season. It is the first time since the Flames moved to Calgary in 1980 that the team has taken at least one point in each of their first five games.
Monahan, Calgary's sixth overall draft pick in the 2013 NHL entry draft, is still eligible to return to Ottawa in the OHL. So far, the rookie seems to be playing like he wants to stay.
Dennis Wideman and Mark Giordano also scored for Calgary (3-0-2). Jiri Hudler had two assists to extend his points streak to five games. The Flames now depart on a five-game road trip that begins Wednesday in Anaheim.
New Jersey poured on the pressure in one stretch past the midway mark of the third period before Monahan's go-ahead goal. But despite Joey MacDonald losing his stick, the Devils were unable to score with Flames' bodies diving in front of shots. Kris Russell, Lance Bouma and T.J. Galiardi all blocked shots during the mad scramble.
Already ahead 2-1 in the second period, New Jersey appeared to have scored again when MacDonald failed to handle Ryan Clowe's slapshot off the wing and the puck bounded up in the air and into the net. The goal was waved off and Devils winger Michael Ryder, who had gone hard to the net for the rebound, was sent off for goalie interference.
Calgary had its best prolonged pressure of the game on the ensuing power play, controlling the puck in the Devils' zone for the entire man advantage. After several close changes, Giordano eventually got his stick on the puck in the slot and poked a backhand into the net behind Brodeur to tie the score.
New Jersey broke a 1-1 tie at 16:03 of the second period when Zubrus beat MacDonald from just inside the blue-line with a slapshot.
Giordano fed a pass across to Wideman on Calgary's third power play and he one-timed a slapshot inside the goal post while Curtis Glencross screened Brodeur.
New Jersey struck first at 13:58 of the first, shortly after a power play expired.
MacDonald made a pad stop on Damien Brunner but the rebound zipped into the slot. Henrique buried it for his first of the year.
Notes: Calgary's Lee Stempniak had his four-game points streaks snapped. ... David Jones (upper body) did not play. He has been placed on injured reserve and is considered week-to-week. Tim Jackman made his season debut in his place. ... Monahan turns 19 on Saturday. ... New Jersey's Jacob Josefson made his season debut after being a healthy scratch the first four games. He was inserted for Andrei Loktionov. ... The game featured two teams that have started the season in opposite directions. The Flames had yet to lose in regulation in four games while New Jersey was one of two teams still still looking for its first win.