A garment, such as a jacket, having extensible sleeves, is described. The garment has an outer layer comprising a torso portion having two armholes, two sleeve portions, and an optional collar portion. An action back configuration enables the sleeves to extend. An action back has a flange of material at least partially tucked within each of the armholes. An elastic connector couples the two flanges and extends across the back portion of the garment. When a person reaches forward the flanges extend to provide additional material for the extension of the sleeve. In addition, the two sleeves are configured with a gusset having two substantially linear sides connected to the sleeve and a curvilinear side coupled to the armhole. The gusset may have a cut to allow the gusset to stretch. The sleeves comprise a cuff having a thumbhole for maintaining the cuff over the thumb of a wearer.