To date, genome-wide association studies (GWAS) of endometrial cancer have identified 16 genetic risk regions; however, candidate susceptibility genes at these regions are yet to be confirmed. We performed a transcriptome-wide association study (TWAS) to identify candidate endometrial cancer susceptibility genes and provide evidence to support previously identified candidate genes. To maximise statistical power, we used a multi-tissue TWAS approach, integrating the largest endometrial cancer GWAS (12,906 cases and 108,979 controls of European ancestry) with cis-expression quantitative trait loci (eQTLs) from 48 tissues. Identified genes were prioritised by colocalisation analysis to reduce false positive findings. We found seven candidate endometrial cancer susceptibility genes, six of which had previously been identified as candidate susceptibility genes by parallel functional analyses. The remaining identified gene was a lncRNA located at a potentially novel endometrial cancer genetic risk region. Using phenome-wide association approaches, we found these genes associate with traits related to endometrial cancer risk factors, including cardiovascular phenotypes, diabetes, and hormone levels. This analysis additionally identified associations with traits related to bone health, haematopoiesis and liver function, providing avenues for future study. Comparing genetically predicted endometrial cancer gene expression with drug-induced gene expression profiles from the Connectivity Map database, we identified 14 drug repurposing candidates including tubulin inhibitors, a drug class already in use for treatment of advanced endometrial cancer. In summary, using TWAS we have identified candidate endometrial cancer susceptibility genes and provided evidence to prioritise existing candidates. Follow-up analyses have revealed further potential risk factors for endometrial cancer and compounds that could be repurposed for endometrial cancer treatment. Citation Format: Tracy A. O'Mara, Pik Fang Kho, Gabriel Cuellar Partida, Amanda B. Spurdle, Dylan M. Glubb. Multi-tissue transcriptome-wide association study identifies genetic mechanisms underlying endometrial cancer susceptibility [abstract]. In: Proceedings of the AACR Virtual Special Conference: Endometrial Cancer: New Biology Driving Research and Treatment; 2020 Nov 9-10. Philadelphia (PA): AACR; Clin Cancer Res 2021;27(3_Suppl):Abstract nr PR003.