There is a common agreement that bracing is appropriate for curves between 20 and 40° for the Cobb angle during growth, but for larger curves, the experts’ opinions are not consistent. We designed this systematic review to report the updated evidence about the effectiveness of bracing in scoliosis patients with curves ≥40° and a residual growth period. We included randomized controlled trials, non-randomized controlled trials, prospective and retrospective observational studies, and case series addressing the effect of bracing in patients with idiopathic scoliosis during growth with curves ≥40° for the Cobb angle, published from 2000 onwards. Outcome: The percentage of patients with surgery, curves above 45° or 50°, and a Cobb angle change are all included in the study. Nine papers (563 patients, average worst curve of 44.8°) are included: four are retrospective case series, two are retrospective and two are prospective cohort studies, and one is a prospective controlled study. The overall quality was good, with respect to the type of design. A total of 32% of the patients improved, 26% were stable, and 42% worsened. The rate of improvement ranged from 11% to 78%; the rate of worsening ranged from 4% to 64%. There are some studies suggesting the use of bracing even in the case of severe curves when patients are motivated by trying to avoid surgery. More and better-quality research with coherent outcome criteria is needed.