IMPORTANCE Sexting is the exchange of sexual messages, photographs, or videos via technological devices and is common and increasing among youth. Although various studies have examined the association between sexting, sexual behaviors, and mental health, results are mixed. OBJECTIVE To provide a meta-analytic synthesis of studies examining the associations between sexting, sexual behavior, and mental health using sex, age, publication date, and study methodological quality as moderators. DATA SOURCES Electronic searches were conducted in April 2018 in MEDLINE, PsycINFO, Embase, and Web of Science, yielding 1672 nonduplicate records. STUDY SELECTION Studies were included if participants were younger than 18 years and an association between sexting and sexual behaviors or mental health risk factors was examined. DATA EXTRACTION AND SYNTHESIS All relevant data were extracted by 2 independent reviewers. Random-effects meta-analyses were used to derive odds ratios (ORs). MAIN OUTCOMES AND MEASURES Sexual behavior (sexual activity, multiple sexual partners, lack of contraception use) and mental health risk factors (anxiety/depression, delinquent behavior, and alcohol, drug use, and smoking). RESULTS Participants totaled 41 723 from 23 included studies. The mean (range) age was 14.9 (11.9-16.8) years, and 21 717 (52.1%) were female. Significant associations were observed between sexting and sexual activity (16 studies; OR, 3.66; 95% CI, 2.71-4.92), multiple sexual partners (5 studies; OR, 5.37; 95% CI, 2.72-12.67), lack of contraception use (6 studies; OR, 2.16; 95% CI, 1.08-4.32), delinquent behavior (3 studies; OR, 2.50; 95% CI, 1.29-4.86), anxiety/depression (7 studies; OR, 1.79; 95% CI, 1.41-2.28), alcohol use (8 studies; OR, 3.78; 95% CI, 3.11-4.59), drug use (5 studies; OR, 3.48; 95% CI, 2.24-5.40), and smoking behavior (4 studies; OR, 2.66; 95% CI, 1.88-3.76). Moderator analyses revealed that associations between sexting, sexual behavior, and mental health factors were stronger in younger compared to older adolescents. CONCLUSIONS AND RELEVANCE Results of this meta-analysis suggest that sexting is associated with sexual behavior and mental health difficulties, especially in younger adolescents. Longitudinal research is needed to assess directionality of effects and to analyze the mechanisms by which sexting and its correlates are related. Educational campaigns to raise awareness of digital health, safety, and security are needed to help youth navigate their personal, social, and sexual development in a technological world.