The social amoeba Dictyostelium discoideum is a versatile biological model widely used in drug discovery and studying cellular stress responses. However, its application for cytotoxicity evaluation of natural products, particularly algal-derived compounds, remains underutilized. In this study, we developed a high-throughput developmental assay in D. discoideum to analyze the cytotoxicity of acetone and methanol extracts from the Peruvian seaweed Glossophora kunthii. Our results showed that the acetone extract caused a transient delay in the social development of the amoeba. In contrast, the methanol extract exhibited no significant effects, even at high extract concentrations. UHPLC/Orbitrap/ESI/MS/MS analysis tentatively identified ten major compounds, including pachydictyol A and dictyotriol A diacetate. The presence of diterpenes, such as dictyotadiol and pachydictyol A, previously reported to exhibit moderate cytotoxic activity, likely explains the developmental delay observed with the acetone extract. This study highlights the utility of D. discoideum as a scalable cytotoxicity screening platform within algal pharmacognosy, facilitating the early identification of non-toxic marine natural products suitable for further biomedical and biotechnological development.