Background: Although dual blockade HER2-based neoadjuvant chemotherapy is associated with excellent outcomes for human epidermal growth factor receptor 2 (HER2)-positive breast cancer, pertuzumab is not available to all patients due to cost. The optimal neoadjuvant chemotherapy for HER2-positive breast cancer in the presence of a single HER2 blockade is unknown. This study aimed to compare the efficacy and safety of epirubicin/cyclophosphamide followed by docetaxel/trastuzumab (EC-TH) with docetaxel/carboplatin/trastuzumab (TCH) neoadjuvant setting for HER2-positive breast cancer under the single HER2 blockade. Methods: Patients with stage II-IIIC HER2-positive breast cancer were randomly assigned to either eight cycles of EC-TH every 3 weeks during all chemotherapy cycles, or six cycles of TCH every 3 weeks. The primary endpoint was pathological complete response (pCR) (defined as the absence of invasive tumor cells in breast and axilla, ypT0/is ypN0). Results: From May 2017 to November 2019, 140 patients were randomly assigned, and 135 patients were ultimately found evaluable for the primary endpoint. The pCR was recorded in 25 of 67 patients [37.3%; 95% confidence interval (CI), 25.8–50.0] in the EC-TH group and in 38 of 68 patients (55.9%, 95% CI, 43.3–67.9) in the TCH group (p = 0.032). The most common adverse events (AEs) were neutropenia in 24 of 67 (35.8%) patients in the EC-TH group versus 27 of 68 (39.7%) in the TCH group (p = 0.642), anemia in 33 of 67 (49.3%) patients in the EC-TH group versus 34 of 68 (50.0%) in the TCH group (p = 0.931), and thrombocytopenia in five of 67 (7.5%) patients in the EC-TH group versus 17 of 68 (25.0%) in the TCH group (p = 0.006). Conclusion: For patients receiving the single HER2 blockade trastuzumab for HER2-positive breast cancer, TCH regimen might be a preferred neoadjuvant therapy. Trial registration: This trial was registered with ClinicalTrials.gov identifier: NCT03140553) on 2 May 2017. © The Author(s), 2021.