Abstract Seaweeds demonstrate original and interesting nutritional characteristics. Protein concentration ranges from 5% to 47% of dry basic. Its value depends particularly on species and the environmental conditions. Seaweed protein is a source of all amino acids, especially glycine, alanine, arginine, proline, glutamic, and aspartic acids. In algae, essential amino acids (EAAs) represent almost a half of total amino acids and their protein profile is close to the profile of egg protein. In case of non-EAAs, all three groups (green, brown, and red seaweeds) contain the similar amount. Red seaweed seems to be a good source of protein because its value reaches 47%. The issue of protein malnutrition supports the trend to find a new and cheap alternative source of protein. Algae could play an important role in the above-mentioned challenge because of relatively high content of nitrogen compounds. Algae may be used in the industry as a source of ingredients with high nutritional quality.