The study sought to determine the effect of bank regulation and level of nonperforming loans in commercial banks in Nakuru County Kenya. The specific objectives of the study were to explore the effect of capital adequacy on the level of nonperforming loans in commercial banks in Nakuru County Kenya, to find out the effect of asset quality on the level of nonperforming loans in commercial banks in Nakuru County Kenya, to evaluate the effect of liquidity management on the level of nonperforming loans in commercial banks in Nakuru County Kenya, to examine the effect of management efficiency on the level of nonperforming loans in commercial banks in Nakuru County Kenya and to determine the moderating effect of macroeconomic factors on the relationship between bank regulation and level of nonperforming loans. The literature review focused on portfolio theory of investment, capital asset pricing theory and the capital buffer theory of capital adequacy. The primary data was collected using structured questionnaires and secondary data was collected from the banking survey 2017 and central bank of Kenya annual supervisory reports. The study employed multiple linear regression analysis and the finding revealed that there exist a negative and statistically insignificant relationship between capital adequacy and non-performing loans. It was also observed that there exist a negative and statistically insignificant relationship between liquidity management and non-performing loans. On the other hand, there exist a positive and statistically significant relationship between asset quality and non-performing loans. Similarly, there exist a positive and statistically insignificant relationship between management efficiency and non-performing loans. Finally, the findings indicated that macroeconomic factors have moderating effect on the relationship between bank regulations and non-performing loans in commercial banks in Nakuru County. It was concluded that asset quality positively influences non-performing loans while management efficiency influence positively the non-performing loans. Similarly, liquidity management exerts a negative influence on non-performing loans. Finally, capital adequacy influence negatively on non-performing loans. The study recommends that Central Bank of Kenya should regularly access lending behavior to ensure compliance with banking regulations to avoid increasing incidences of non-performing loans. In addition, Central Bank of Kenya should closely monitor banks with deteriorating asset quality. Further, Central Bank of Kenya should strictly monitor the economic sector and ensure that banks provide adequate provisions for loans to mitigate risks of default. Furthermore, banks should maintain a good balance on deposits and lending out loans and adhere to regulators decisions about monetary policies. Finally, banks should increase the operational efficiency of operation weakness and improve corporate governance on the sanction of loans and Central Bank of Kenya should focus on managerial performance in order to detect banks with potential increases in non-performing loans.