Gadolinium is applied in various industries, such as nuclear technologies, metallurgy, in luminescent material, superconductor production, etc. As result of this extensive usage, gadolinium in stable and radioactive forms is released in the environment, affecting the quality of water. Due to the increasing application of gadolinium in technological processes, the biosorption and bioaccumulation of gadolinium by Arthospira platensis in batch experiments was examined. In biosorption experiments, the influence of pH, gadolinium concentration, time of contact and temperature on Arthospira platensis sorption capacity was investigated. The maximum biosorption capacity of 101 mg/g was attained at a pH of 3.0 and temperature of 20 °C. A pseudo-first-order model was applicable to describe the kinetics of the biosorption and the Freundlich model to explain the equilibrium of the process. In the bioaccumulation experiments, gadolinium ions were almost completely accumulated from the cultivation medium and stimulated biomass growth. Arthospira platensis is of interest for the development of the technology of gadolinium-contaminated wastewater remediation.