The situation has aggravated poverty and brought about untold hardship particularly for the unemployed. Currently, there is intense debate regarding the adjustment in the statutory age of retirement in Nigeria. To that end, a deterministic compartmental mathematical model is designed to study the implication of the proposed increase in the national statutory age of retirement on the national output and the trend of unemployment in Nigeria. The mathematical interpretation of the compartments of the model leads to the corresponding first-order ordinary differential equations. The resulting equations are proved to satisfy the basic features of a good mathematical model. The unemployment-free equilibrium is derived and the stability analysis is performed via stability theory of nonlinear differential equations. Numerical simulation is conducted to validate the analytical results. Results from the simulation show that increasing the national statutory age of retirement will limit the rate at which individuals are moving from the unemployed state to the employed state but widen the rate at which individuals are joining and remaining in the unemployed state.