Malignancy is a risk factor for splanchnic vein thrombosis (SpVT). Data on the natural history of cancer-associated SpVT are limited. This was a single-center retrospective cohort study of 581 adult patients with cancer and SpVT. We aimed to characterize the impact of thrombocytopenia on major bleeding and progression or recurrence of SpVT within one year of initial cancer-associated SpVT diagnosis. Baseline thrombocytopenia (platelet < 100,000/uL within 15 days of SpVT diagnosis) was present in 39.5% of patients. A total of 39.2% of patients received therapeutic anticoagulation within two weeks of SpVT diagnosis. The cumulative once-year incidence of major bleeding was 10.7% (95% CI: 8.2-13.2), and for SpVT recurrence/progression was 16.2% (95% CI: 13.2-19.2). In multivariable regression analysis, therapeutic anticoagulation was associated with increased major bleeding (aRR: 1.74, 95% CI: 1.08-2.81) and decreased progression/recurrence of SpVT (aRR: 0.55, 95% CI: 0.35-0.86). Baseline thrombocytopenia was not independently associated with either major bleeding (aRR: 0.76, 95% CI: 0.43-1.34) or progression/recurrence of SpVT (aRR: 1.14, 95% CI: 0.73-1.78). A secondary analysis using inverse probability of treatment weighting with propensity scores for baseline thrombocytopenia corroborated that patients with thrombocytopenia did not have increased bleeding risk (aHR: 0.81, 95% CI: 0.48-1.39). Multivariable analysis treating platelets as a time varying covariate also did not reveal an association with major bleeding (aHR: 0.89, 95% CI: 0.55-1.45). Bleeding and thrombosis progression were frequent in patients with cancer-associated SpVT. Anticoagulation was associated with increased major bleeding and decreased thrombotic progression; thrombocytopenia did not impact outcomes.