The black-lipped pearl oyster Pinctada margaritifera is of high economic importance in French Polynesia. Arecent decline in pearl value led to the initiation of several genetic breeding programs aiming to improve production traits, including oyster shell growth, which dictates the time of grafting, size of the implanted nuclei, and biomineralization capacities. We assessed shell diameters on hatchery-produced spat to analyze juvenile growth performance of four half-sib families derived from polyandry (one dam crossed with two sires) and polygyny (two dams crossed with one sire) using gametes obtained by thermal shock or gonad scarification. Spat growth was monitored over 3 mo, with shell diameter measured weekly. Results revealed that the spawning method had no significant effect on juvenile growth; however, the half-sib families produced with the polygyny mating design showed significant differences in average shell diameter between dams throughout the experiment, whereas none were observed between sires with the polyandry mating design. Precocious larval size selection within each family was performed by separation into batches of small, medium, and large size, and their maintenance through juvenile stages, providing the possibility for early growth selection. These findings are important for genetic breeding programs (1) as breeding of sires and dams exhibiting the most colorful inner shell phenotypes would be possible with the gonad scarification spawning procedure without affecting overall growth performance and (2) because P. margaritifera is a protandrous hermaphrodite species, genetic selection strategies in the pearl industry must take into account the differential influence of polygyny and polyandry mating designs.