The cyanobacterium Spirulina platensis is widely recognized as a "food of the future" due to its rich composition of bioactive compounds, including phycobilins, carotenoids, unsaturated fatty acids, and proteins, which contribute to its medicinal and nutritional value. This study aimed to optimize biomass production by evaluating the effect of urea supplementation and seawater incorporation into the growth medium. A modified Zarrouk medium with 0.15 mg/L urea (MZU) was found to enhance S. platensis growth more effectively than the standard Zarrouk medium. Furthermore, combining urea with a modified Zarrouk-Provasoli's seawater (PESW) mixture (50:50 v/v) resulted in the highest biomass yield and pigment accumulation, demonstrating the potential of seawater as a partial replacement for conventional freshwater-based media. The use of urea as a nitrogen source proved to be a cost-effective strategy for boosting biomass production while maintaining high levels of valuable bioactive compounds. These findings provide valuable insights for large-scale S. platensis cultivation, particularly in regions with limited access to fresh water. The study underscores the potential of urea-seawater combinations in improving S. platensis productivity, supporting its application in sustainable food production, nutraceuticals, and biotechnology industries.