Individual (mass) selection for shell height was carried out in the Chilean oyster, Ostrea chilensis. The selection was based on the shell height of oysters, 30 months old, which came from the natural population of the Quempillen River Estuary (Southern Chile). Divergent selection was applied, three selected groups were chosen to mass spawn (high, mean selected, and low). Offspring from the mean selected and low groups were obtained. A statistically significant difference (p < 0.05) was detected in shell height at 30 months between the offspring of the mean selected and low selected group, suggesting the presence of additive gene effects for growth rate. The realized heritability estimate (h2 = 0.34 ± 0.12) for a decrease in the shell height, indicates that selective breeding on this trait can be effective in Ostrea chilensis.