The Fanconi anemia pathway orchestrates the repair of DNA inter-strand crosslinks and stalled replication forks. A key step in this pathway is UBE2T and FANCL dependent monoubiquitylation of the FANCD2-FANCI complex. The Fanconi anemia pathway represents an attractive therapeutic target because activation of this pathway has been linked to chemotherapy resistance in several cancers. However, very few selective inhibitors of ubiquitin conjugation pathways are known to date. By using a high-throughput screen compatible assay, we have identified a small molecule inhibitor of UBE2T/FANCL-mediated FANCD2 monoubiquitylation that sensitizes cells to the DNA cross-linking agent, carboplatin.