Background: Neoadjuvant therapy combining docetaxel, trastuzumab and pertuzumab (DTP) was compared to trastuzumab emtansine (T-DM1) in the randomised phase II PREDIX HER2 trial. Patients, ≥18 years with HER2 positive breast cancer, ≥20mm or with verified lymph node metastases, were randomised to six courses of DTP (Standard group) or T-DM1 (Experimental group) before surgery. After operation patients in the Standard arm received two, and those in the Experimental arm four courses of EC. Since there were no differences in proportions of complete response at surgery and in the event-free survival between the groups, health-related quality of life (HRQoL) is of special interest. Methods: HRQoL was measured, using European Organization for Research and Treatment of Cancer (EORTC) QLQ-C30 + EORTC QLQ-BR23, before randomisation, after six courses before surgery, at three months and one year after surgery. Results: Response rate for the questionnaires varied between 87% and 99% for the 198 included patients. There were no between-group differences at baseline. Results after six courses revealed statistically significant differences (p≤0.01), favouring the Experimental group on 12 out of 21 of the EORTC QLQ-C30 and BR23 variables (Physical-, Role-, and Social- functioning, Global quality of Life, Fatigue, Dyspnea, and Diarrhea, Body image, Sexual functioning, Sexual enjoyment, Systemic therapy side effects and Upset by hair loss). Three months after surgery, however, statistically significant differences in favour of the Standard group were found for six variables (Physical functioning, Nausea/vomiting, Dyspnea, Constipation, Systemic therapy side effects, Upset by hair loss). No other between group differences were found with one exception: lower levels of Breast symptoms in the Experimental group. One possible explanation is that patients in the Experimental group were still on chemotherapy at that assessment point, whereas the majority in the Standard group had terminated their treatment. No differences were found between the groups at the one-year after surgery follow-up, where the levels on most variables had returned to baseline values. Conclusions: HRQoL was better in the Experimental group during neoadjuvant treatment. Three months after surgery, however, HRQoL was in favour or the Standard arm. HRQoL returned to baseline levels for most variables at the one-year follow-up and no between-group differences were found. Clinical trial information: NCT02568839.