In some coastal areas, large quantities of beach-cast macroalgae can accumulate and are usually considered waste and disposed of. However, due to their biofunctional and nutritional properties, they have great potential as a new source of raw materials. Increasing population growth has made the search for alternative raw materials with valuable nutritional properties urgent; here, beach-cast macroalgae could provide great potential. Our research goal was to characterize the nutritional profile of 12 beach-cast seaweed species from the Brazilian coast to assess their potential valorization. A considerable number of nutritional compounds was observed, such as ash (6.5–59.3%), total dietary fibers (22.1–65.8%), proteins (5.1–21.5%), and carbohydrates (31.4–81.0%), with an expressive abundance of minerals, free amino acids, and fatty acids. Spatoglossum schroederi and Alsidium seaforthii showed protein contents of 21.5 ± 0.2%, 19.7 ± 0.1%, and high amounts of total dietary fiber of 59.2 ± 0.4%, 61.7 ± 4.9%, respectively. The overall profile suggests that beach-cast seaweeds are suitable for nutritional and other bioeconomical purposes, to which different species with different characteristics contribute. Contamination of these seaweeds with unwanted toxic compounds like micropollutants was not studied. However, this must be considered before they are used for human consumption.