Meta-aramid fibers (MAF) are widely used in high-performance applications due to their exceptional thermal and mechanical properties. However, their poor dyeability and lightfastness remain significant challenges. This study investigates the effects of ultraviolet (UV) exposure on MAF dyed with disperse and vat dyes, focusing on UV absorption, photodegradation, and mechanical performance. Through physicochemical characterizations, we reveal that vat dyes exhibit superior UV absorption due to their higher benzene ring content, leading to enhanced lightfastness. However, this increased UV absorption generates more free radicals, accelerating fiber degradation and mechanical deterioration. The lightfastness ratings of vat-dyed MAF (rating of 3–4) surpass those of disperse-dyed counterparts (rating of 2), despite a greater breaking strength loss (23–25 vs. 11%). These findings elucidate the trade-off between color stability and mechanical resilience in MAF dyeing. This study provides valuable insights for optimizing dye selection in high-durability applications, ensuring both longevity and aesthetic integrity in extreme environments.