This work describes for the first time the larval and postlarval development of the razor clam Ensis siliqua, and aimed to standardize the techniques for hatchery production of this species' seed. The larvae were obtained from the induced spawning of a group of broodstocks under controlled laboratory conditions. Five larval batches per duplicate were cultured to produce postlarvae for nursery culture. Unfertilized eggs of E. siliqua were brown and spherical, and measured from 76.9–99.3 µm in diameter in the different larval batches. Fifteen-day-old larvae settled when a size of 361.5–414.8 µm was reached. Larval survival ranged between 20.0–52.7%, with an average of 39.4%. Mortality was high from settlement until 1 mo of cultivation. The razor clam seed reached lengths of 20.9 ± 2.7 mm and 39.0 ± 4.0 mm at 3 mo and 6 mo, respectively. Substrate experiments during nursery culture showed that better survival was achieved when spat cultures were performed without substratum.