Kenny Cooper and Mehdi Ballouchy also scored as the Red Bulls won their second straight at home after losing their opening two games on the road. New York has nine goals since returning home, with Henry getting five and two assists.
Sanna Nyassi and Justin Mapp scored for winless Montreal (0-3-1). The Impact, who had one goal in their first three games, had leads of 1-0 and 2-1 before the Red Bulls' French international took over.
The Red Bulls' win did not come without a cost. Midfielder Rafa Marquez suffered a groin injury and didn't play in the second half.