<b><i>Context:</i></b> Treatment with growth hormone (GH) is considered effective in improving adult height (AH) in Turner syndrome (TS). However, there are few studies comparing AH between treated patients and a concurrent untreated group. <b><i>Objective:</i></b> To assess the efficacy of GH treatment in improving AH in TS and to review previous published studies with treated and untreated groups. <b><i>Participants and Methods:</i></b> We retrospectively analyzed clinical data and AH of a large cohort of GH-treated (<i>n</i> = 168) and untreated (<i>n</i> = 131) patients with TS. Data are shown as median and interquartile range (IQR). We assessed pretreatment variables related with AH and compared our results with 16 studies that also included an untreated group. <b><i>Results:</i></b> The GH-treated group was 6.2 cm taller than the untreated group (AH = 149 cm [IQR 144.5–152.5 cm] vs. 142.8 cm [IQR 139–148 cm], <i>p</i> &#x3c; 0.001) after 4.9 years of GH treatment with a dose of 0.35 mg/kg/week. AH SDS corrected for target height (TH) was 7.2 cm higher in GH-treated patients. AH SDS ≥−2 was more frequent in GH-treated patients (43%) than in untreated patients (16%, <i>p</i> &#x3c; 0.001). AH SDS was also more frequently within the TH range in the GH-treated group (52%) than in the untreated group (15%, <i>p</i> &#x3c; 0.001). Height SDS at start of GH therapy and TH SDS were positively correlated with AH (<i>p</i> &#x3c; 0.001; <i>R</i>² = 0.375). Considering the current result together with previous similar publications, a mean AH gain of 5.7 cm was observed in GH-treated (<i>n</i> = 696) versus untreated (<i>n</i> = 633) patients. <b><i>Conclusions:</i></b> Our study strengthens the evidence for efficacy of GH therapy in patients with TS from different populations.