The red alga Mastocarpus stellatus is widely found on the coastline of Brittany (France) and it was previously reported to contain high amounts of floridoside, a well-known glycoside in red algae. Therefore, we aimed at evaluating the potential interest of M. stellatus for industrial purposes. Floridoside extraction was optimized, hydroethanolic mixture being the most efficient extractant compatible with industrial requirements. Floridoside yield was increased significantly through pre-treatment and conditioning of the alga before extraction. Thus, salt stress and drying procedure both resulted in an increase in floridoside concentration. Studies of seasonal variations of floridoside content in this species showed that maximal levels were recovered in autumn. We now propose an optimized procedure for M. stellatus valorization, especially for biomedical applications.