Objectives To examine the degree to which states' work hour regulations for nurses—policies regarding mandatory overtime and consecutive work hours—decrease mandatory overtime practice and hours of work among registered nurses. Methods We analyzed a nationally representative sample of registered nurses from the National Sample Survey of Registered Nurses for years 2004 and 2008. We obtained difference‐in‐differences estimates of the effect of the nurse work hour policies on the likelihood of working mandatory overtime, working more than 40 hours per week, and working more than 60 hours per week for all staff nurses working in hospitals and nursing homes. Principal Findings The mandatory overtime and consecutive work hour regulations were significantly associated with 3.9 percentage‐point decreases in the likelihood of working overtime mandatorily and 11.5 percentage‐point decreases in the likelihood of working more than 40 hours per week, respectively. Conclusions State mandatory overtime and consecutive work hour policies are effective in reducing nurse work hours. The consecutive work hour policy appears to be a better regulatory tool for reducing long work hours for nurses.