The embryonic and larval developmental stages of the geoduck clam Panopea globosa were described, and the size at different ages post-fertilization were evaluated using both shell length (SL) and shell height (SH). Gametes were obtained from wild ripe broodstock and fertilized under controlled conditions (22.15°C, 35‰, pH8.4). Fertilization and meiosis were confirmed by single membrane formation (after ∼5–10 min) and extrusion of the first polar body (after ∼15–20 min), respectively. Trochophore larvae (94.80 ± 0.74 µm SL and 82.92 ± 4.69 µm SH) were observed 17.5 h after fertilization. Veliger larvae (146.36 ± 17.54 µm SL and 121.78 ± 15.96 µm SH) were observed 43 h after fertilization. Umbo growth was apparent 7 days after fertilization, and pediveliger larvae (355.36 ± 20.99 µm SL and 313.64 ± 21.24 µm SH) developed 21 days after fertilization. The growth of SH and SL were best described by a linear function of time (T = days) from fertilization to the pediveliger stage (SL = 12.04 T + 81.40 and SH = 10.69 T + 67.33). The linear relationship between SL and SH indicates that the rate of SH growth during larval development of P. globosa is smaller than that of SL (SH = 0.875, SL = -2.20). The results demonstrate that highly uniform larvae sizes can be obtained from spawning runs in controlled environmental conditions. This is the first description of the development of P. globosa from the embryonic stage to early juvenile stages.