Supplementation of dairy products with non-dairy ingredients with the aim of increasing the concentration of particular nutrients is a common industrial practice. In the present study, a semi-hard cheese was supplemented with each of five seaweeds (Himanthalia elongata, Laminaria ochroleuca, Porphyra umbilicalis, Ulva lactuca, Undaria pinnatifida). Addition of 10 g of dehydrated seaweed per kg of curd caused significant differences in dry matter and pH value, but it hardly influenced cheese microbiota. Antioxidant activity, which was correlated with total phenolic compounds, was significantly higher in cheese supplemented with H. elongata than in control cheese. Instrumental colour and texture parameters of cheese varied significantly with the added seaweed species. Cheeses supplemented with H. elongata, U. pinnatifida and L. ochroleuca received odour and flavour quality scores from panellists that did not differ from those of the respective control cheese until day 60 and were associated with low seaweed odour and flavour scores.