Can increasing women's use of digital financial services raise their empowerment? We test this hypothesis using a randomized control trial with 152 female microfinance groups in Tanzania, where treated groups were randomly switched from cash to mobile money loan repayment. This exogenous increase in women's use of mobile money leads women to expand their use for other types of transactions, including business payments and saving. Women's control over their finances increases and they are more empowered within the household. Over time, women's businesses become more profitable. These findings highlight the benefits of shifting payments to digital for women.