Sagkeeng First Nation's adolescent breastfeeding educational session was evaluated using a randomized pretest-posttest control group design. The intervention group received the session first; the control group received the session following the posttest. A retention test to measure overall retained learning was given to all students 10 days later. Breastfeeding beliefs increased (mean +/- SD = 41.9 to 47.0, P = .0047) from pretest to posttest for intervention subjects but not for controls. There were no changes in bottle-feeding beliefs or breastfeeding attitudes. There was an increase in breastfeeding beliefs from pretest to retention test for all students (true treatment effect [TTE] = .85 standard deviation units [SDU], P = .004). Learning was gender specific, with females experiencing increases in breastfeeding beliefs (TTE = 1.12 SDU, P = .004), decreases in bottle-feeding beliefs (TTE = -.77 SDU, P = .04), and a trend to increased breastfeeding attitudes (TTE = .41 SDU, NS). Males showed small, inconsistent learning effects. Learning occurred in the areas of health, convenience, cost, and decreased embarrassment.