Background and study aims Upper gastrointestinal bleeding (UGIB) from malignancy is associated with high rebleeding and mortality rates. Recently, TC-325 powder has shown promising results in the treatment of UGIB, including malignant bleeding. The aim of this study was to compare the efficacy of TC-325 versus best clinical management. Patients and methods From August 2016 to February 2020, all patients with evidence of UGIB from malignancy were randomized to receive TC-325 therapy or control group, in which endoscopic treatment was not mandatory. Exclusion criteria were hemoglobin drop without overt bleeding and UGIB from non-tumor origin. The primary outcome was 30-day mortality. Secondary outcomes were 30-day rebleeding, blood transfusion and length of hospital stay. Results Sixty-two patients were randomized, three were excluded and 59 were included in the final analysis (TC-325 group = 28; control = 31). Groups were similar at baseline. Active bleeding was observed in 22 patients in the TC-325 group and 19 in the control group ( P  = 0.15). Successful initial hemostasis with TC-325 was achieved in all cases. Additional therapy (radiotherapy, surgery or arterial embolization) was equally performed in both groups (42.9 % vs 58.1 %; P  = 0.243). There were no differences in 30-day mortality (28.6 % vs. 19.4 %, P  = 0.406) or 30-day rebleeding rates (32.1 % vs. 19.4 %, P  = 0.26). Logistic regression identified no significant predictors of rebleeding. Age, Eastern Cooperative Oncology Group (ECOG) score 3 to 4 and AIMS65 score > 1 predicted greater mortality. Conclusions TC-325 was effective in achieving immediate hemostasis in malignant gastrointestinal bleeding but did not reduce 30-day mortality, 30-day rebleeding, blood transfusion or length of hospital stay. Age, ECOG 3-4, and AIMS65 > 1 were predictive factors of mortality.