The aging of the skin is considered a cumulative process that is classed as intrinsic or extrinsic. Environmental factors like sun exposure and air pollution are considered the main cause of extrinsic aging. Mainly, intrinsic aging reflects the genetic background and depends on time. Spirulina platensis unicellular blue–green algae have a variety of biological and nutritional activities because of their high level of nutrients. The current study aims to investigate the mechanism by which spirulina extract (SE) may act anti-aging in female albino rats. Spirulina extract (20 mg/mL) was injected subcutaneously before UVA irradiation (2.16 J/cm2), daily for 7 days. The epidermal thickness and the collagen fibers layer were stained utilizing hematoxylin and eosin and Masson