In the workplace, women can experience stereotyping and marginalization as a result of their gender (Eagly & Carli, 2007; Gipson, Pfaff, Mendelsohn, Catenacci, & Burke, 2017). Having allies, or people who are supportive of or who advocate for an oppressed group can help members of marginalized communities to achieve personal and social success (Drury, 2014; Evans & Washington, 1991). The Men’s Allyhood toward Women in the Workplace (M.A.W.W.) measure seeks to evaluate men’s supportiveness of women in the workplace, enabling researchers and practitioners to understand and improve the climate for women at work. The M.A.W.W. was first developed with the input of five subject matter experts who commented on the clarity and relevance of a list of 84 proposed items. The item pool was pared down from 84 items to 59 which were then subjected to an exploratory factor analysis. The exploratory factor analysis narrowed the item pool from 59 to seventeen items. Although it was hypothesized that the M.A.W.W. would yield six factors, only three factors were supported by the analysis: Knowledge & Awareness, Action, and Skills & Capacity. These three factors showed internal consistency reliabilities that ranged from acceptable to excellent. A confirmatory factor analysis then led to the deletion of two more items, yielding a total of fifteen items for the final, three-factor version of the M.A.W.W. Convergent validity of this final measure was demonstrated by positive correlations with scales assessing affirming attitudes toward women in general. Evidence of divergent validity was shown with negative correlations with scales assessing negative and prejudicial attitudes against women. Furthermore, construct evidence was demonstrated with statistical analysis showing no correlation between the M.A.W.W. and a personality scale.