Background: Active malignancy is a well described risk factor for thrombosis. Randomized clinical trials (RCT) have evaluated anticoagulation (AC) with DOACs or LMWH for prevention of VTE in ambulatory cancer patients. This objective of this meta-analysis is to evaluate the efficacy and safety of DOACs and LMWH thromboprophylaxis in adult patients with active solid organ malignancy or lymphoma. Methods: We conducted a search of MEDLINE, EMBASE, and CENTRAL from 10/31/2009-11/31/2019. Data for meta-analysis was extracted from studies that met inclusion criteria (RCT, ambulatory patients age >18 years with active solid organ malignancy or lymphoma, prophylactic AC with DOAC or LMWH). Risk ratio (RR) were calculated for primary (efficacy) end point of VTE occurrence and secondary (safety) end points of major bleeding (MB) and clinically relevant non-major (CRNMB). Subgroup analyses of efficacy and safety endpoints were conducted based on AC and cancer types. Results: Eleven trials met inclusion criteria with total of 7741 participants. Two trials evaluated DOACs and nine trials evaluated LWMH for thromboprophylaxis. Efficacy results are noted in Table. Safety outcomes for MB and CRNMB for AC were RR 1.83 (95% CI 1.26, 2.65), p=0.001 and RR 1.36 (95% CI 1.05, 1.76), p=0.02. Safety outcomes for MB and CRNMB for DOAC were RR 1.95 (95% CI 0.88, 4.30), p=0.10 and RR 1.35 (95% CI 0.80, 2.27), p=0.26. Safety outcomes for MB and CRNMB for LMWH were RR 2.05 (95% CI 1.19, 3.51), p=0.009 and RR 1.44 (95% CI 1.01, 2.05), p=0.04. Conclusions: Both DOACs and LMWH decrease risk for VTE development in ambulatory adult cancer patients. MB and CRNMB were significantly increased in patients taking LMWH but not in patients taking DOACs. A large clinical trial using DOACs for thromboprophylaxis would help elucidate the thrombosis and bleeding event rate in ambulatory cancer patients.