Purpose <p>To evaluate the effectiveness of nighttime brace treatment in boys with adolescent idiopathic scoliosis (AIS) compared to girls according to brace adherence and curve progression.</p> Methods <p>Children with predominantly thoracolumbar/lumbar AIS curves 15–40° at Risser stages 0–2 treated with Providence nighttime bracing from 2015 to 2019 were retrospectively reviewed until skeletal maturity or surgery. Outcomes included brace adherence using iButton temperature sensors, curve progression, and progression to a surgical threshold of 45°, compared between boys and girls. Propensity-matched analysis of one male to one female by initial Risser stage, curve magnitude, and curve location further explored bracing outcomes.</p> Results <p>Patients included 66 boys and 241 girls. At brace prescription, boys were older (13.8 ± 1.5 vs. 12.3 ± 1.2&#xa0;years, p &lt; 0.001) but did not differ by curve magnitude (24 ± 4° vs. 24 ± 4°, p = 0.656) and BMI (18.5 ± 2.8 vs. 18.1 ± 2.7&#xa0;kg/m², p = 0.271). During bracing, boys grew more (12 ± 8 vs. 9 ± 6&#xa0;cm, p = 0.007) but did not differ by total curve progression (increase of 4 ± 12° vs. 2 ± 9°, p = 0.562), curve improvement ≥ 6° (17% vs. 20%, p = 0.602), curve progression ≥ 6° (32% vs. 29%, p = 0.662), and progression to surgery (9% vs. 5%, p = 0.259). Adherence was not statistically different between boys (6.4 ± 2.5&#xa0;h) and girls (7.0 ± 2.4&#xa0;h, p = 0.087). Propensity-matched groups did not differ by bracing outcomes.</p> Conclusion <p>Contrary to full-time bracing literature, boys with predominantly thoracolumbar/lumbar AIS treated with Providence nighttime bracing did not differ significantly in brace wear adherence, curve progression, or progression to surgery compared to girls.</p>