INTRODUCTION: This multicenter, randomized, double-blind, placebo-controlled phase 2 trial compared the efficacy, and safety of adding pyrotinib to trastuzumab, docetaxel, and carboplatin versus placebo, trastuzumab, docetaxel, and carboplatin in Chinese patients with human epidermal receptor 2 (HER2)-positive early or locally advanced breast cancer (ClinicalTrials.gov identifier: NCT03756064). METHODS: Sixty-nine women with HER2-positive early (T1-3, N0-1, M0) or locally advanced breast cancer (T2-3, N2 or N3, M0; T4, any N, M0) were recruited from October 1, 2019, to June 1, 2021. Before surgery, patients received 6 cycles of orally pyrotinib (400 mg once per day), trastuzumab (8-mg/kg loading dose and 6-mg/kg maintenance doses), docetaxel (75 mg/m2), and carboplatin (AUC = 6 mg/mL·min) or orally placebo, trastuzumab, and docetaxel, and carboplatin every 3 weeks. The primary end point was independent review committee-assessed total pathologic complete response rate. The 2-sided Cochran-Mantel-Haenszel test, stratified by age, hormone receptor status, tumor stage, nodal status, cTNM stage, and Ki-67 level was used to compare rates between treatment groups. RESULTS: In total, 69 female patients were randomized (pyrotinib, 36; and placebo, 33; median age, 53 [31-69] years). In the intention-to-treat population, total pathologic complete response rates were 65.5% (19/29) in the pyrotinib group and 33.3% (10/30) in the placebo group (difference, 32.2%, p = 0.013). Diarrhea was been reported in 86.1% of patients (31/36) in the pyrotinib group as the most common adverse events (AEs) and 15.2% of patients (5/33) in the placebo group. But no grade 4 or 5 AEs were reported. CONCLUSION: Treatment with pyrotinib, trastuzumab, docetaxel, and carboplatin resulted in a statistically significant improvement in the total pathologic complete response rate versus placebo, trastuzumab, docetaxel, and carboplatin for the neoadjuvant treatment of HER2-positive early or locally advanced breast cancer in Chinese patients. Safety data were in line with the known pyrotinib safety profile and generally comparable between treatment groups.