Aim: The study aims to investigate attitudes and perceptions influencing fish consumption in a sample of clinical trial participants and compare these perceptions to those expressed by a sample of adults not involved in the trial. Methods: Six semi-structured focus groups were conducted; three with participants of a weight loss trial which incorporated specific and general fish consumption advice (n = 15) and three with nontrial participants from the same study population (n = 14). All data were recorded digitally and transcribed verbatim by the moderator. Data analysis was carried out using NVivo (QSR International Pty Ltd, Melbourne, Victoria, Australia). Factors influencing fish consumption were coded into a number of sub-themes and themes. Results: The main factors that influenced fish consumption were health impact, the cost of consuming fish and seafood products, the physical and sensory characteristics of fish, food preferences of family members, and the culinary positions of fish and seafood. Conclusion: This study highlighted attitudes and perceptions that may influence fish consumption. A clinical trial incorporating dietetic intervention appeared to influence the importance participants placed on nutrition education; however, additional practical strategies may be required to address barriers to consumption such as perceived price and availability.