Little of the research involving individuals undergoing testing for BRCA1/2 mutations has examined the effect of genetic counseling and testing on diet, exercise, and vitamin use. This study examined diet, exercise, and vitamin use among 120 Ashkenazi Jewish individuals with a personal and/or family history of breast and/or ovarian cancer who presented for BRCA1/2 genetic counseling and testing. Health behaviors were measured at pre-counseling and 6 months post-results. T-tests or ANOVAs were used to test for association of health behaviors with potential predictors: personal cancer history, anxiety, perceived cancer risk, gene status, and perceived efficacy of health behaviors. Multivariable linear regression analysis found gender (P = .007) and perceived efficacy of a healthy diet (P = .005) to be significantly associated with healthy food consumption; gender (P = .003), education (P = .01), and personal cancer history (P = .02) were significantly associated with unhealthy food consumption; higher age (P < .001) and perceived efficacy (P < .001) were significantly associated with higher vitamin use. Paired t-tests found no significant changes in diet, vitamin use, and exercise as a result of genetic counseling and testing. We conclude that genetic counseling and testing had little impact on health behaviors. Rather, perceived efficacies of certain health behaviors to prevent or delay cancer may be more reliable predictors of those behaviors. Clinicians should assess perceived efficacies of health behaviors in their interventions to improve healthy practices in the BRCA1/2 genetic testing population.