We report on the proportion of maturity stages as a function of size of the Pacific sharpnose shark Rhizoprionodon longurio. Based on the development of internal and external organs, males and females were classified as immature or mature. A logistic model was fitted to develop a maturity curve to estimate the length at which 50% of the individuals are mature (L 50%). This species has an annual reproductive cycle and its birthing season is from April to July, with June as the main month. For males, L 50% = 100.61 cm total length (TL) and = 2.57, and for females, L 50% = 92.9 cm TL and = 1.08. For pregnant females, L 50% = 106.4 cm TL and = 6.11. The maturity curves obtained in the present study can be used in demographic studies to produce more accurate forecasts of the population reproductive rate and thus develop fishery management measures for this species.