An online survey was conducted to investigate the influence of varying product stimuli on the perception of overall appeal, tastiness, healthiness, and environmental benefit of plant-based (PB) meat alternatives (PBMAs) and plant-based fish alternatives (PBFAs) among 1407 adult British consumers. The written product stimuli varied across three factors: 1) referencing ‘vegan’ or ‘plant-based’, 2) referencing animal products or animal-like use or neutral pre-cooked descriptor, and 3) information about the source of the PB ingredient (‘soy’ or ‘pea/ rice’). The results revealed moderate ratings for both products, with PBMAs generally being perceived more favourably than PBFAs. Modest effects of the design factors were observed, with the most consistent effects attributed to the source of the PB ingredient. Products labelled as ‘made from pea and rice’ were perceived more favourably than those labelled ‘made from soybeans’ across all attributes for both PBMAs and PBFAs. The term ‘to be used like meat/fish’ led to slightly more favourable ratings mainly for overall appeal in both product types. Additionally, for PBFA products, labelling as ‘plant-based’ was slightly more favourably received than ‘vegan,’ whereas no such effect was observed for PBMAs. A strong and consistent effect of participants’ dietary habits was also observed, with vegetarians and vegans generally rating PBMAs and PBFAs more favourably than omnivores and flexitarians. Taken together, these findings suggest that product names and descriptions, especially with regard to ingredient transparency, and dietary habits may play significant roles in shaping consumer perceptions of PB alternatives to meat and fish.