Background: Patients with R/M ESCC failing platinum-based chemotherapy have grave prognosis. Anti PD-1 immune-checkpoint inhibitors (ICIs), by demonstrating survival benefits over 2^nd-line chemotherapy in multiple phase III trials, have emerged as a new standard-of-care for patients with platinum-refractory R/M ESCC. However, the efficacy of anti-PD-1 ICIs remains modest with an objective response rate (ORR) of 17-20%; and the median overall survivals (OS) for these patients range from 8.2 to 10 months. Cabozantinib, a multikinase inhibitor, in combination with atezolizumab has been investigated in the phase Ib COSMIC-021 trial, which includes multiple cohorts of various cancer types including gastroesophageal cancer and head-and-neck cancer. Promising preliminary results were reported in lung cancer and genitourinary cancer cohorts. To investigate the combination of cabozantinib plus atezolizumab in patients with ESCC, a subtype of esophageal cancer that may be under-represented in the gastroesophageal cancer cohort of COSMIC-021 trial, we thus proposed this phase II trial to verify the hypothesis whether adding cabozantinib to atezolizumab would improve the outcomes of R/M ESCC patients who have failed platinum-based chemotherapy. Methods: This single institution single-arm phase II study includes patients with histologically confirmed R/M ESCC who failed at least one platinum-based chemotherapy. Patients with prior exposure of any ICI or kinase inhibitor are excluded. Patients enrolled will receive cabozantinib 40mg once per day and atezolizumab 1200mg once every three weeks until disease progression or intolerable toxicities. The primary endpoint of this study is the ORR evaluated by RECIST 1.1; and the key secondary endpoints include progression-free survival, OS, and toxicity profile. We hypothesize that combination of cabozantinib plus atezolizumab will improve the ORR from 15% to 30%. With one-sided, 0.1 type I error (α), 0.2 type II error (β, corresponding power: 0.8), the sample size will be 37. The study, registered with clinical trial ID of NCT05007613, started patient enrollment in Jun 2021. As of Sep of 2021, 5 patients have been enrolled. Clinical trial information: NCT05007613.