Abstract: Bioactive peptides have been widely used in the cosmetics industry due to their easy absorption, strong efficacy, and high safety. The rich resources of marine organisms make the exploration and screening of bioactive peptides from marine sources of significant economic, ecological, and social value. This study analyzed the soothing effects and irritancy of a marine-derived peptide, Scylla paramamosain dodecapeptide (SPD), using LPS-induced inflammation model and SDS-stimulated zebrafish embryonic spinokinesis model. Additionally, multiple skin irritation tests and acute eye irritation tests were conducted to assess the irritancy of SPD. The results from the RAW264.7 inflammation model showed that SPD at concentrations greater than 25 µg/mL effectively inhibited LPS-induced morphological changes in RAW264.7 cells, significantly downregulated the secretion of pro-inflammatory cytokines (TNF-α, IL-6, IL-8, IL-1β) and the inflammatory mediator PGE2 (prostaglandin E2), and upregulated the secretion of the anti-inflammatory cytokine IL-10 in a concentration-dependent manner. In the zebrafish embryo stimulation model, SPD at concentrations of 50 μg/mL and 100 μg/mL effectively alleviated SDS-induced irritation. Furthermore, SPD showed no irritation to the dorsal skin and cornea of New Zealand rabbits, with an average irritation score of 0. These findings demonstrate that SPD possesses significant soothing properties and exhibits no obvious irritation to rabbit skin and eyes, providing a scientific basis for its potential application in cosmetics.