Background: The current standard treatment of primary systemic therapy (PST) in HER2+ breast cancer is anthracyclines and/or taxanes combined with trastuzumab which demonstrates high pathological complete response (pCR). The pCR is considered as a predictive marker of prognosis although results are slightly different depending on the hormone receptor status. The efficacy and tolerability of docetaxel, cyclophosphamide and trastuzumab (HER-TC) as neoadjuvant chemotherapy (NAC) remains unclear. We performed a prospective multicenter study of HER-TC NAC in HER2+ primary breast cancer. Methods: Eligible patients had HER2+ invasive breast cancer that measured more than 1cm, less than 7 cm and N0~N1 clinically between July 2011 and February 2014. Four cycles of HER-TC (6 mg/kg loading dose 8 mg/kg, 75 and 600 mg/m²) were administered intravenously every 3 weeks as NAC. We investigated the pCR of primary breast tumors; pCR was defined as no histological evidence of invasive carcinoma, or the appearance of only ductal carcinoma in situ. Cardiac toxic effects, defined as a decrease in left ventricular ejection fraction (LVEF), were assessed by echo-cardiography at baseline, at the completion of NAC. Results: 42 patients were enrolled. The completion rate for 4 cycles of HER-TC was 97.6 % (41 of 42). Relative dose intensity was 98.0 % for HER-TC therapy. Overall pCR rate was 43.9 % (18 of 41). pCR rate for patients with luminal HER2 (ER+, HER2+), and HER2 enriched ( ER-, HER2+ ) were 40.0 % (8 of 20), and 47.6 % (10 of 21), respectively. pCR was achived with about same probability in each subtype. Mean LVEF at baseline and, the completion of NAC were 66.1% and 64.8%, respectively. Conclusions: Four cycles of HER-TC might be one of the NAC options for HER2 positive breast cancer. There were no patients with decrease in LVEF during the treatment. Clinical trial information: UMIN000013263.