The Mottled Scorpionfish (Pontinus clemensi) is an ecologically and economically important species endemic to the Eastern Tropical Pacific. Despite its importance, little is known about its life history traits. In order to close this knowledge gap, we analyzed otoliths and gonads to describe age and reproduction, fit the von Bertalanffy, logistic, and Gompertz growth models, and selected the most parsimonious model using Akaike Information Criterion. We collected 420 samples from fishing trips throughout the archipelago and fish landed at Pelican Bay dock in Santa Cruz Island from 2013–2015. Fork length of fish ranged from 19–67 cm, with males being significantly larger than females, age ranged from 9 to 17 years (n = 203), with similar ranges for both genders, and the logistic model was the most parsimonious growth model (k₅ = 0.46 in males, 0.28 in females, 0.31 for the species). Spawning-capable females were observed in all months, suggesting fish can reproduce year round, with size at first maturity (L₉₀) occurring at 33.6 cm or 11.8 years for females, and 43.4 cm or 13.7 years for males. Our results suggest that, similarly to other species in this family, P. clemensi is a slow-growing fish that begins reproducing later in life. Considering P. clemensi represents an important resource, a management plan should be urgently introduced to ensure a sustainable fishery and the survival of the population.