Advantages of using intraoperative radiotherapy with electrons (IOERT) as a boosting modality in breast‐conserving therapy include the direct visualization of the tumor bed, a reduced skin dose, and patient convenience. We report oncological outcome, postoperative complication rate, and mammographic changes on follow‐up imaging in women treated at our institution with IOERT as a boost modality in breast‐conserving therapy for early‐stage breast carcinoma. Between January 2007 and June 2018, 763 consecutive patients were enrolled. During breast‐conserving surgery, an IOERT boost of 9 Gy was applied, followed by whole breast irradiation (WBI). At a median follow‐up of 62.2 months (range: 0.5‐135), 13 in‐breast recurrences were observed, yielding a local tumor control rate of 98.4% at 5 years. In multivariable analysis, high tumor grading was predictive for local recurrence (HR = 5.6; 95%CI: 1.19‐26.2). A total of 27 (3.5%) patients developed any kind of postoperative complication. None of the tumor characteristics nor any of the IOERT technical parameters were predictive for development of a postoperative complication. On follow‐up imaging, 145 patients with mammographic changes BIRADS score ≥3 were found of which 50.3% required a biopsy. Only 17 patients had positive biopsies; none of the IOERT parameters were predictive for false‐positive imaging. A 9 Gy IOERT boost combined with postoperative WBI provided outstanding local control rates, was well‐tolerated, with limited postoperative complications. However, radiologists must be aware of a presumable higher prevalence of mammographic changes after IORT as a boost.