Background The programmed death 1 inhibitor toripalimab plus the angio-immuno kinase inhibitor surufatinib showed a tolerable safety profile and preliminary efficacy in patients with advanced solid tumors in a phase I study.Methods This open-label, multi-cohort study in China enrolled patients with advanced solid tumors who had failed or were intolerable to standard treatment into tumor-specific cohorts. Patients received surufatinib (250 mg orally, once daily) plus toripalimab (240 mg intravenously, once every three weeks). Results for three cohorts (gastric/gastroesophageal junction [GC/GEJ] adenocarcinoma, esophageal squamous cell carcinoma [ESCC], and biliary tract carcinoma [BTC]) are reported here. The primary endpoint was investigator-assessed objective response rate (ORR) per Response Evaluation criteria in Solid Tumors version 1.1.Results Between December 17, 2019, and January 29, 2021, 60 patients were enrolled (GC/GEJ, n = 20; ESCC, n = 20; BTC, n = 20). At data cutoff (February 28, 2023), ORRs were 31.6%, 30.0%, and 11.1%, respectively. Median progression-free survival was 4.1, 2.7, and 2.9 months, respectively. Median overall survival was 13.7, 10.4, and 7.0 months, respectively. Overall, grade >= 3 treatment-related adverse events occurred in 28 (46.7%) patients.Conclusions Surufatinib plus toripalimab showed promising antitumor activity and a tolerable safety profile in immunotherapy-na & iuml;ve patients with GC/GEJ adenocarcinoma, ESCC, or BTC. These findings warrant further study in larger randomized trials comparing surufatinib plus toripalimab with standard therapies in these tumors. ClinicalTrials.gov NCT04169672.Conclusions Surufatinib plus toripalimab showed promising antitumor activity and a tolerable safety profile in immunotherapy-na & iuml;ve patients with GC/GEJ adenocarcinoma, ESCC, or BTC. These findings warrant further study in larger randomized trials comparing surufatinib plus toripalimab with standard therapies in these tumors. ClinicalTrials.gov NCT04169672.