This study was carried out to assess whether a prolonged time between primary transurethral resection of non-muscle-invasive bladder cancer (TURB) and implementation of bacillus Calmette-Guerin (BCG) immunotherapy (time to BCG; TTBCG) is associated with adverse oncological survival in patients with T1 high-grade (HG) non-muscle-invasive bladder cancer (NMIBC).