Eco-friendly, cost efficient and effective extraction methods have become significant for the industries applying zero waste principles. The two main objectives of this study were; to examine fucoxanthin extraction from wet Phaeodactylum tricornutum using subcritical fluid extraction and to characterize the residual biomass in order to determine the potential application areas. The highest fucoxanthin yield of 0.69 +/- 0.05 mg/g wet cell weight was achieved using methanol with solvent-to-solid ratio of 200:1 at 120 rpm, 20 MPa pressure and at 35 degrees C for 60 min by subcritical extraction. Microscopy images showed that most of the cells were disrupted and intracellular components were effectively released. Based on the results of energy dispersive spectroscopy, biomass contained a mixture of organic molecules including mainly carbon (57-72%), oxygen (26-41%), magnesium (0.6-1.4%) and silica (0.4-1%) (wt%). These results make the residual biomass a potential candidate for various areas such as bioenergy, material sciences and sensor technologies.