Oncoplastic techniques in breast-conserving surgery (BCS) are used increasingly for larger tumours. This large cohort study aimed to assess oncological outcomes after oncoplastic BCS (OPS) versus standard BCS. Data for all women who had BCS in three centres in Stockholm during 2010-2016 were extracted from the Swedish National Breast Cancer Register. All patients with T2-3 tumours, all those receiving neoadjuvant treatment, and an additional random sample of women with T1 tumours were selected. Medical charts were reviewed for local recurrences and surgical technique according to the Hoffman-Wallwiener classification. Date and cause of death were retrieved from the Swedish Cause of Death Register. The final cohort of 4178 breast cancers in 4135 patients was categorized into three groups according to surgical technique: 3720 for standard BCS, 243 simple OPS, and 215 complex OPS. Median duration of follow up was 64 (range 24-110) months. Node-positive and large tumours were more common in OPS than in standard BCS (P < 0.001). There were 61 local recurrences: 57 (1.5 per cent), 1 (0.4 per cent) and 3 (1.4 per cent) in the standard BCS, simple OPS and complex OPS groups respectively (P = 0.368). Overall, 297 patients died, with an unadjusted 5-year overall survival rate of 94.7, 93.1 and 92.6 per cent respectively (P = 0.350). Some 102 deaths were from breast cancer, with unadjusted 5-year cancer-specific survival rates of 97.9, 98.3 and 95.0 per cent respectively (P = 0.056). Oncoplastic BCS is a safe surgical option, even for larger node-positive tumours, with low recurrence and excellent survival rates.