This study examined the extent to which human resource planning influences secondary school teachers’ productivity in Cross River State, Nigeria. Specifically, it investigated the predictive roles of assessing current manpower, forecasting future manpower needs, and balancing demand with supply on teacher productivity. A predictive correlational research design was adopted, and a stratified random sample of 765 participants (principals and teachers) was drawn from a population of 7,650 public secondary school staff. Data were collected using a researcher-developed questionnaire, the Human Resource Planning and Teachers’ Productivity Questionnaire (HRPTPQ), which demonstrated high reliability (Cronbach’s Alpha coefficients ranging from 0.82 to 0.87). Analysis using simple linear regression revealed that all three dimensions of human resource planning significantly predicted teachers’ productivity, with assessing current manpower, forecasting future needs, and balancing demand with supply collectively explaining a substantial proportion of variance in performance. The study concludes that strategic human resource planning is critical for optimizing teacher performance and enhancing educational outcomes in secondary schools.