Significance: Self-Efficacy theory (SET) proposes that individuals' self-efficacy in a particular context will influence their motivated behavior in that context. SET is comprised of two interrelated variables, self-efficacy (SE) and outcome expectancy (OE; Rodgers & Brawley, 1996). This study uses a previously validated instrument based on SET, the Nutrition-Teaching Self-Efficacy Scale (Brenowitz & Reeves, 2003), to investigate the influence of a professional development program aimed at teaching healthy behavior concepts on teachers' efficacy in teaching nutrition in their classrooms. Design: Participants were 38 (29 female, 9 male), mostly Caucasian (50%), American Indian (29%), or African-American (13%); and either a K-12 classroom (31) or Physical Education (7) teacher. Teachers were assigned to participant (N=27) and control (N=11) groups. Participants completed a previously validated instrument based on SET theory that demonstrated high levels of internal consistency reliabilities in this sample (all Cronbach's alphas >.82). The factor structure also showed an adequate fit of the model to the data. All participants completed the instrument pre and post; also, the program teachers completed the instrument four times throughout the school year. Repeated Measures Analyses of Variance (RM-ANOVA) was used to examine teachers' nutritional efficacy, outcome expectations for students, and overall SE. Results: There were no differences between the groups at pretest. Significant differences were found in nutrition efficacy between experimental and control teachers at post test (F(1, 30) = 4.89, p<.035, eta squared = .14) suggesting that teachers who participated in the professional development experiences became more efficacious in their ability to teach nutritional concepts to their students. RM-ANOVAs results for the program group differences over time indicated that teachers' self-efficacy for teaching nutrition increased Wilks' Lambda F(3, 66)=3.22, p<.01. Follow-up ANOVAs tests showed significant differences in nutritional efficacy and overall SE, with no significant changes in outcome expectancy or self-reported frequency of teaching. Results suggest that the professional development program had a positive affect on teachers' efficacy related to teaching nutrition in this context. Program teachers showed significant positive changes in their self-efficacy for teaching nutrition over control teachers as well as significant increases in SE over time. This study provides support for the ability of professional development experiences to positively influence the SE of teachers for teaching nutritional concepts, a critical component in the battle against the obesity crisis. Keyword(s): community-based programs, multiculturalism/cultural diversity, nutrition