Introduction <p>Post-inflammatory hyperpigmentation (PIH) is common and distressing in skin of color. Ultraviolet (UV) radiation and visible light (VL) exacerbate PIH, yet most sunscreens do not target the oxidative and inflammatory pathways that drive it.</p> <p>This study evaluated a broad-spectrum sunscreen with sclareolide and niacinamide for mitigating PIH induced by combined UV/VL exposure and inflammatory stimuli.</p> Methods <p>In an investigator-masked, randomized, intra-individual study, 20 participants with Fitzpatrick skin types IV–V underwent controlled UV/VL exposure with or without tape stripping. The test product was applied daily for 20&#xa0;days. The primary endpoint was change in ΔITA° at Day 22; clinical pigmentation/erythema and colorimetry (Δ<i>L</i>*, Δ<i>a</i>*, Δ<i>b</i>*, Δ<i>E</i>) were secondary endpoints.</p> Results <p>The sunscreen significantly prevented pigmentation at all protected sites. In stripped, exposed zones, protected skin improved by + 5.96 ΔITA° versus − 9.88 ΔITA° in unprotected skin (net protection ~ 16 ITA°, <i>p</i> &lt; 0.001). In non-stripped, exposed areas, the difference was + 11.76 ΔITA° (<i>p</i> &lt; 0.001). Secondary endpoints improved by 48–87%. No adverse events were reported.</p> Conclusions <p>A broad-spectrum sunscreen with sclareolide and niacinamide mitigates PIH induced by inflammation and VL in darker phototypes. These findings support preventive use in PIH-prone populations. Comparative studies with and without these ingredients are warranted.</p> Clinical Trial Registration <p>This study was registered with ISRCTN under the identifier ISRCTN11448711.</p>