This study aims to Statistically Evaluate the Role of Political Interference on Public Policy Effectiveness in Nigeria and determine whether there is a positive evidence-based relationship between the variables under study.  A quantitative cross-sectional research design was adopted using structured questionnaire for data collection. Sample was obtained using Krejcie and Morgan's sampling formula. Data were analysed using descriptive statistics, Pearson correlation, Ordinary Least Squares (OLS) regression, hierarchical multiple regression, moderation analysis and structural equation modelling (SEM). The findings revealed that Political interference, Executive directive intensity and procurement interference intensity exert statistically significant negative effect on policy effectiveness with bureaucratic capacity significantly moderating the PI-PES relationship, attenuating the negative effect under high-capacity conditions. Aligning with the views of Woodrow Wilson, the practical implications of this study highlight the need for the Nigerian government and other leaders in Africa at large to delink politics from policy process as this will ensure smooth policy implementation. This study is novel especially as it delved deeper using empirical data to examine political interference on public policy in Nigeria. It advances principal-agent and neo-patrimonial theory by quantifying the moderating role of bureaucratic capacity, providing empirical grounding for policy reforms.