Abstract: This paper uses the introduction of the Benazir Income Support Program in Pakistan to study the impact of unconditional cash transfers on married women's labor supply. Using a fuzzy regression discontinuity design, the paper provides evidence of a positive, significant impact of the transfer on the labor supply of married women without children, but no significant impact on the labor supply of married women with children. These findings are at odds with standard household labor supply models that predict a negative impact of unearned income on labor supply. Instead, I argue, that they are in keeping with models in which gender norms restrict women's ability to enter the workforce. Cash transfers can increase female bargaining power and help them overcome restrictive norms. The paper finds evidence for this: the transfer significantly increases women's control over household funds and their mobility outside the home. Further, dividing households into more or less constrained in terms of the gap between male and female attitudes towards female labor force participation, it finds an increase in labor supply for more constrained households and no impact for less constrained households. These findings, however, are only evident five years into the program. Data concerns makes it difficult to determine whether this is a dynamic effect or an issue of selection. The paper deals extensively with this concern, providing suggestive evidence for the former.