The objective of the study was to investigate the relationship between strategic planning and performance of NGOs in Machakos County, with a case study of Mission for Essential Drugs and Supplies. The study’s anchor theory was Ansoff’s Strategic Performance Theory, supported by Resource-Based View Theory and Stakeholder Theory. The study adopted a descriptive research design, with a target population of 200 respondents drawn from Mission for Essential Drugs and Supplies in Machakos. A sample size of 133 respondents was selected using a stratified random sampling technique. Data were collected using questionnaires and analyzed using descriptive statistics, correlation analysis and regression analysis. The study results showed that the implementation of strategic planning significantly impacts the performance of NGOs. Regression analysis results showed a correlation coefficient of (R = 0.737), suggesting a strong positive relationship between strategic planning and NGO performance. The coefficient of determination (R²) was 0.543, indicating that changes in strategic planning account for 54.3% of the variance in NGO performance. The study concludes that there is a substantial correlation between NGOs' performance and strategic planning hence improving it will result to positive performance. The study recommends that MEDS's management and board of directors should continue designing and adopting policies, rules, processes, governing structures, and strategic plans in line with their objectives.