INTRODUCTION: Transgender/gender-diverse (TGD) youth are treated with gonadotropin-releasing hormone agonists (GnRHa) to halt endogenous puberty and prevent the development of secondary sex characteristics discordant with their gender identity. This treatment may have significant impact on growth and height velocity (HV). METHODS: Participants were recruited prior to GnRHa initiation from four gender specialty clinics in the United States. Anthropometric, laboratory, and Tanner-stage data were abstracted from medical records. RESULTS: Fifty-five TGD youth (47% designated male at birth) with a mean ± standard deviation age of 11.5 ± 1.2 years were included in the analysis. HV in the first year of GnRHa use was median (interquartile range) 5.1 (3.7 – 5.6) cm/year. Later Tanner stage at GnRHa initiation was associated with lower HV: 5.3 (4.4 – 5.6) cm/year for Tanner stage II, 4.4 (3.3 – 6.0) cm/year for Tanner stage III, and 1.6 (1.5 – 2.9) cm/year for Tanner stage IV (p = 0.001). When controlled for age, there was not a significant difference in mean HV between TGD youth and pre-pubertal youth; however, when stratified by Tanner stage individuals starting GnRHa at Tanner stage IV had a HV below that of prepubertal youth (1.6 (1.5 – 2.9) vs. 6.1 (4.3 – 6.5) cm/year, p =0.006). CONCLUSIONS: Overall, TGD youth treated with GnRHa have HV similar to that of prepubertal children, but TGD youth who start GnRHa later in puberty have a HV below the pre-pubertal range. Ongoing follow-up of this cohort will determine the impact of GnRHa treatment on adult height. IMPLICATIONS AND CONTRIBUTIONS: This study describes the HV in the first year of GnRHa treatment in pubertal participants in a large multi-site cohort of TGD youth in the United States. Overall, TGD youth treated with GnRHa have HV similar to that of prepubertal children, but TGD youth who start GnRHa later in puberty have a HV below the pre-pubertal range.