Most hospital staff nurses' work schedules extend beyond the typical 9:00 a.m. to 5:00 p.m., Monday through Friday workday, to provide continuous nursing care to patients. Simultaneously, most hospitals in the United Counties exclusively use 12-hour shifts. Thus, staff nurses who work overtime may work more than 12 hours within 24 hours and return to work quickly without sufficient rest and sleep. Nurses' fatigue may continue the following work regardless of regular or overtime shifts. Working overtime among nurses is a prevalent practice used to control chronic understaffing and a standard method used to handle normal patient census variations. According to the 2004 National Sample Survey of Registered Nurses (NSSRN), more than 40% of Kenya registered community health nurses (KRCHN) worked more than 40 hours per week [21]. According to the ministry of health, fifty-four percent of the respondents to the 2018 NSSRN worked more than 39 hours per week in their principal nursing position (2010). The purpose of this study was two-fold. The first step was to examine the relationship between mandatory nurse overtime regulations and nurse injuries and adverse patient events. The second step was to assess the mediating effect of nurse overtime on the relationship between the regulations and outcomes after controlling for other nurse work characteristics. A cross-sectional design was used, incorporating data from staff RNs working in hospitals in two counties (Kakamega & Bungoma). A sample size above 250 is suggested by Cohen's guidelines [13]. SPSS version 22.0 and Stata version 10 were used for the data analysis. Univariate, descriptive statistical analyses were conducted to examine the sample characteristics; 15.6% of RNs worked mandatory overtime (either paid or unpaid) while 34.1% worked voluntary overtime (either paid or unpaid) in a typical week. In the current study, the associations between mandatory overtime regulations and nurse and patient outcomes among a sample of 173 nurses in Kakamega and Bungoma were examined. Findings indicated that mandatory nurse overtime regulation did not have any association with nurse injuries. On the other hand, there were statistically significant associations found between the regulations and adverse patient events. The findings of this study should be viewed with the following limitations in mind. Even though the sample was selected randomly to represent the population in both Counties, and the Dillman Tailored Design Method with three survey mailings and reminder postcards was used in an attempt to increase the response rate and to recruit a sufficient sample to ensure the statistical power, the final response rate was 29.8% (226 RNs). Given this response rate, it is impossible to generalize the study findings due to the potential for self-selection bias among respondents. This study did not find any relationship between mandatory overtime regulations and nurses' overtime hours. As a result, although there were significant relationships between the regulation and adverse patient events, the regulations did not impact patient outcomes. Mandatory overtime regulations were not related to nursing injuries.