CONTEXT: Early initiation of growth hormone (GH) therapy is recommended for short children born small for gestational age (SGA); however, real-world data indicate that treatment is often delayed. OBJECTIVE: We aimed to assess the impact of patient age at GH therapy initiation on long-term growth outcomes and safety in short children born SGA. METHODS: Analysis of pooled data from NordiNet® International Outcome Study (NCT00960128; 469 European clinics) and the ANSWER Program (NCT01009905; 207 US clinics), two large, complementary observational studies. Patients received GH as prescribed by their treating physician. Enrolled patients born SGA were categorized into three groups based on their age at GH treatment initiation: 2 to <4 years, 4 to <6 years, and ≥6 years. Patient characteristics at birth and GH initiation, auxology, and safety data were evaluated. RESULTS: The effectiveness analysis (treatment-naïve and prepubertal patients at GH initiation) included 3318 patients: 10.7% aged 2 to <4 years at therapy initiation, 31.6% aged 4 to <6 years, and 57.7% aged ≥6 years. Following 8 years of therapy, the mean improvement in height standard deviation score from baseline was significantly greater in the 2 to <4 years group vs the 4 to <6 years (+2.5 vs +2.2; P = 0.0054) and ≥6 years groups (+2.5 vs +1.7; P < 0.0001). No unexpected safety events were reported. CONCLUSION: Early initiation of GH therapy in short children born SGA may be an important contributor to height optimization. The data are reassuring regarding the long-term safety of GH therapy in this population.