Haliotis kamtschatkana is the only abalone native to the Pacific Northwest of North America. Haliotis kamtschatkana populations are in decline, and current restoration efforts in Washington State rely on out-planting hatchery-produced juveniles. Hatchery personnel report highest mortalities in the postlarval stage of H. kamtschatkana, mainly during the first 3 to 6 months. Postlarvae feed on films of benthic diatoms, and the purpose of this study was to test six diatom species (Achnanthes brevipes, Amphora salina, Amphiprora paludosa, Cylindrotheca closterium, Navicula incerta, and Nitzschia laevis) as suitable diets for H. kamtschatkana. Diatom diet suitability might rely on several factors, including diatom characteristics as well as the postlarva's ability to ingest the diatoms. The radula is a crucial feeding structure for gastropods and may display morphological plasticity, but this has never been characterized in H. kamtschatkana. We investigated survival, growth, and radula morphology of H. kamtschatkana postlarvae when fed one of six benthic diatom species for 61 days post-settlement. Amphora salina yielded the highest survival, in a statistically homogenous subgroup with N. incerta, A. paludosa, and C. closterium. Achnanthes brevipes yielded exceptionally low survival, on par with a starvation control. Cylindrotheca closterium yielded significantly better growth than all other diets except A. salina. Radula development was similar to that of other abalone species. The shape and size of the radula did not explain success or failure of any of the diatom diets since the radula morphology of H. kamtschatkana was comparable to other abalone that have succeeded when fed these same diets. We found no relationship between diatom diet and radula morphology. We recommend A. salina as a suitable diet for newly settled H. kamtschatkana postlarvae, and that a combination of A. salina and C. closterium be used to supplement feeding on naturally occurring biofilms.