The study was carried out to evaluate three microalgae as potential nutrient sources in diets for monogastric animals. In a digestibility experiment with adult mink (Mustela vison), the microalgae Nannochloropsis oceanica, Phaeodactylum tricornutum and Isochrysis galbana were fed at 60, 120 and 240 g kg^-1 as is, replacing fish meal. The N. oceanica and P. tricornutum had similar crude protein (CP) content (47.7 and 49.0% of DM, respectively), amino acid composition and lipid content (8.4 and 7.4%, respectively), whereas I. galbana contained 20.1% CP and 16.2% lipids. There was a significant linear reduction in CP digestibility with increasing dietary inclusion of all algae products. The apparent CP digestibility determined by linear regression for N. oceanica, P. tricornutum and I. galbana was 35.5, 79.9 and 18.8%, respectively. The individual amino acid digestibilities showed acceptable values for P. tricornutum, but low and highly variable values for N. oceanica and I. galbana. Although the algae contributed a minor proportion of dietary lipids, lipid digestibility declined with increasing inclusion of all algae and especially with the highest level of N. oceanica. It was concluded from the mink study that among the investigated algae, P. tricornutum was the preferable source of digestible nutrients.