This quantitatively driven sequential mixed methods study articulates the role of theory in mixed methods research and assesses the contribution of a mixed methods design to examining gender differences in men and women’s genetic testing decisions and the psychosocial factors impacting health-seeking behaviors post-testing. A quantitative online survey of BRCA-positive mutation men and women was followed by a qualitative component consisting of semi-structured telephone interviews regarding genetic testing and post-testing decision making. Findings reveal gender differences in testing motivations: women focus on health; men focus on their family’s needs. Gender differences also appeared in psychological states and surgical decisions, revealing women’s more negative psychosocial reactions to a positive BRCA test result and higher rate of selecting preventative surgery.