Human populations in the Caribbean region, suffer recurrently for 12 years from brown tides followed by significant strandings of Sargassum spp. which cause environmental, economic and health issues. Given current interest in new renewable sources of chemicals, proteins, and polymers, this underexploited biomass represents a potential source to be explored in a biorefinery concept. Up the value chain in biorefinery process, seaweeds should be rapidly stabilised. Stabilisation by drying would permit to reduce the storage and transport costs and to obtain a product stable all year round. The aim of this work was to investigate oven drying and air impingement drying at two air velocities (7 and 21 m s−1) on three species of Sargassum: S. fluitans III, S. natans I and S. natans VIII. The drying kinetics were studied. The apparent diffusivity coefficients were calculated thanks to the Fick’s diffusional model. Seven thin-layer equations were used to fit drying kinetics, namely Page, Modified Page, Diffusion approach, Verma, Two-term, Midilli-Kucuk and Henderson-Pabis modified. Freeze-drying, as a reference drying method, was applied on Sargassum in order to compare the effects of drying processes on several phytochemical components, which are neutral sugars, proteins, polyphenols, uronic acids and mineral matter. According to these results, air impingement drying was the better process to dry these three Sargassum species, but it also depended on the seaweed chain of valorisation after the stabilisation process.