Consumers are concerned about antibiotic and ractopamine usage; therefore, alternatives need to be found. Objectives of this study were to investigate the effects of using seaweed as an alternative feed supplement and comparing performance, carcass, pork quality, and immune traits in pigs fed seaweed, control, and ractopamine diets. Pigs were allocated to one of three treatments (CON, SWE, RAC) at weaning (n = 40/treatment). Pigs were weighed every two weeks. Carcass characteristics, pork quality, and immune data were collected post-mortem. No differences were found between treatments for feed intake, growth, or feed efficiency. Pigs on RAC treatment had greater hot carcass weight and dressing percentage (P < 0.05). Chops from RAC pigs were lighter (P = 0.05), less red (P < 0.05), and tougher (P = 0.08). There were no differences between treatments for FABP2 gene expression, cell proliferation percentages, or crypt depths. Therefore, no negative effects of feeding seaweed to pigs were found in this study.