The need to rebuild Pacific ocean perch, Sebastes alutus, populations on the west coast of the United States has precipitated a need to better understand the life history characteristics of this rockfish species. One such characteristic is mating behavior, which has the potential to influence the amount of genetic diversity in a population. We documented and examined the frequency of multiple mating in Pacific ocean perch collected off the Oregon coast using five microsatellite loci. We found that 47 of 66 (71.2%) females examined had broods sired by multiple males. The mean number of sires per brood was 1.92 (SD = 0.76) and ranged from 1–4. Polyandrous females were significantly larger and had an older average age than monogamous females. Our results suggest that polyandrous behavior among female Pacific ocean perch off the coast of Oregon is prevalent, is related to female size and age, and should be preserved by maintaining a natural age structure in this population.