James Justin Acker (born September 24, 1958) is an American former Major League Baseball pitcher who played from 1983 to 1992.

On July 6, 1986, Acker was traded by the Blue Jays to the Atlanta Braves for pitcher Joe Johnson.

On August 24, 1989, Acker was traded by the Braves back to the Toronto Blue Jays for Francisco Cabrera and Tony Castillo.

Acker spent part of the 1989 year and the complete 1990 and 1991 seasons back with the Blue Jays.

[1] Acker ended his baseball career after six appearances with the Oklahoma City 89ers, the Texas Rangers Triple-A affiliate, in 1993.