He was traded to the Boston Bruins in 1937 and then loaned to the New York Americans in 1938-39. After that Jackson played for six straight seasons with the Bruins, winning the Stanley Cup in 1941, He hit a career high with 28 goals and 41 assists in 1943-44.
In the middle of the 1944-45 season was traded back to the Toronto Maple Leafs. He retired at the end of the season after winning the Stanley Cup one more time.
After the November 15, 1942 game at Detroit, it was discovered that the jersey of Tony Graboski of the Montreal Canadiens was missing. With no extra jerseys and an impending game at the Boston Garden, the Canadiens borrowed the #16 jersey from the Red Wings which goalie Paul Bibeault wore for the November 17, 1942 game against the Boston Bruins. Graboski wore Bibeault's #1 jersey for the game.