<p><i>Background</i>: Problematic social media use, particularly TikTok, has raised growing concern due to its potential negative effects on young people’s mental health. Addressing this phenomenon requires valid and reliable psychometric instruments. In Latin America—especially in Peru—validated measures specifically designed to assess TikTok addiction are still lacking, limiting rigorous understanding of the problem and hindering comparisons with international findings in digital mental health research. <i>Objective</i>: To adapt and psychometrically validate the TikTok Addiction Scale (TTAS) in a sample of Peruvian adolescents and young adults, examining its factorial structure, reliability, measurement invariance, and concurrent validity. Methods: An instrumental study was conducted with 797 Peruvian TikTok users (M = 22.37; SD = 4.17), applying the TTAS and the PHQ-9. Confirmatory factor analyses were performed, along with reliability estimation (<i>ω</i>), measurement invariance by sex and age, and concurrent validity analysis using structural equation modeling (SEM). <i>Results</i>: The six correlated-factor model showed good fit (CFI = 0.96; TLI = 0.95; RMSEA = 0.078), with factor loadings ranging from 0.63 to 0.94. Dimensional reliability was adequate (<i>ω</i> = 0.69 to 0.93). Configural, metric, scalar, and strict invariance across sex and age was confirmed (ΔCFI ≤ 0.01). Concurrent validity was supported by significant associations between TTAS and depressive symptoms (<i>β</i> = 0.26 to 0.52; CFI = 0.984; RMSEA = 0.043). <i>Conclusions</i>: The Spanish version of the TTAS is a valid and reliable instrument for assessing TikTok addiction among Peruvian youth. Its availability strengthens digital mental health assessment in Latin America and facilitates cross-cultural comparisons with the international literature.</p>