Objective: Gender minority youth (i.e., children/adolescents whose gender identity and/or expression is inconsistent with their birth-assigned sex) experience elevated rates of emotional and behavioral problems relative to cisgender youth (who identify with their birth-assigned sex), which are not intrinsic to gender identity but attributable to unique minority stressors. Although empirically supported treatments have proven effective in treating these mental health concerns generally, randomized controlled trials have not examined effects for gender minority youth. Method: To address this gap, we pooled data from clinically referred youth (N = 432; M(SD)age = 10.6(2.2); 55.1% White) assigned to empirically supported treatment conditions across four previous randomized controlled trials of modular psychotherapy. A proxy indicator of gender identity (i.e., youth’s wish to be the opposite sex) was used to classify gender minority (n = 64) and cisgender (n = 368) youth. Youth- and caregiver-reported pretreatment internalizing and externalizing problems, treatment effectiveness on these domains, and treatment acceptability were compared across groups. Results: Gender minority youth reported more severe pretreatment internalizing and externalizing problems compared to cisgender youth; in contrast, their caregivers reported less severe problems. Although treatment was equally effective for both groups on most outcomes, gender minority youth’s caregiver-reported externalizing problems improved more slowly and less reliably, and their self-reported internalizing problems were more likely to remain clinically elevated. Furthermore, gender minority youth reported lower treatment satisfaction. Conclusions: While findings suggest that empirically supported treatments may effectively address many mental health problems for gender minority youth, they also underscore the need for treatment enhancements that improve acceptability and outcomes. (PsycInfo Database Record (c) 2020 APA, all rights reserved)