Background: Patients with borderline resectable esophageal squamous cell carcinoma have poor prognosis and poor response to first-line therapy. The BRES-1 study aimed to assess the efficacy and safety of camrelizumab combined with chemotherapy in patients with borderline resectable esophageal squamous cell carcinoma. Methods: This single-center, single-arm prospective phase II clinical trial will enroll 30 patients with borderline resectable esophageal squamous cell carcinoma. The 30 enrolled patients will receive preoperative camrelizumab with chemotherapy regardless of programmed death ligand-1 status. Preoperative therapies will include camrelizumab, nab-paclitaxel and cisplatin. Surgery will be performed 3-4 weeks after the completion of the preoperative neoadjuvant therapy. Three weeks after surgery, two periods of maintenance therapy will be continued with camrelizumab combined with chemotherapy. Then, maintenance treatment will be continued with camrelizumab up to one year. Primary endpoints included pathologic complete response (pCR), major pathological response (MPR). Results: As of September 15, 2022, 19 patients who met the criteria were enrolled (63% males, median age 67), neoadjuvant therapy was completed in 18 patients and ongoing in 1 patients. Among the 19 patients, 11 patients were resected and all patients underwent an R0 resection. 5 patients (45%) reached major pathologic response, 3 patients (27%) reached pathologic complete response, 8 patients (8/11, 73%) with complete regression (TRG 1) or near-complete regression (TRG 2). No grade 3-4 immunotherapy related AEs were observed, no surgery related mortality. The most common treatment-related AEs were leukopenia (18/19, 95%), lymphopenia (18/19, 95%) and anaemia (15/19, 79%). Conclusions: Camrelizumab with chemotherapy for borderline resectable esophageal squamous cell carcinoma has shown good conversion rates. Its efficacy and safety will be further investigated in later trials. Clinical trial identification: ChiCTR2200056728.