Tissera, KM, Naughton, GA, Gabbett, TJ, Krause, LM, Moresi, MP, and Benson, AC. Sex differences in physical fitness characteristics and match-play demands in adolescent netball: Should male and female adolescents co-compete in netball? J Strength Cond Res 33(3): 846-856, 2019-Sports participation offers multifaceted benefits, especially during adolescence. However, policies relating to male and female adolescents co-competing in team sports can be prohibitive and lack an evidence base. This study aimed to strengthen evidence on coparticipation of male and female adolescents playing recreational netball. Off-court fitness characteristics (power, speed, agility, and high-speed intermittent running) and match-play performances from global positioning system (GPS) and video analysis were compared in adolescent males (n = 34, mean ± SD, age, 15.2 ± 0.8 years) and females (n = 45, mean ± SD, age, 14.9 ± 0.7 years), with previous recreational netball experience. Independent t-tests showed adolescent men outperforming females in all off-court fitness characteristics (p < 0.001). Two-way analyses of variance explored sex-based interactions in match-play (GPS accelerometer data and notational analyses) and type of competition (mixed-/single-sex formats) in forty-two 7-minute matches. Overall, no differences in match-play performances were found between males and females (p > 0.05). Notational skill-based comparisons showed that male skills were better in mixed- than single-sex matches. Conversely, competition format did not alter skills of females. Despite more netball experience in females and superior off-court fitness characteristics in males, on-court performance differences between males and females were minimal in these recreational adolescent netball players. Coparticipation in netball was not detrimental to the performance of either sex.