Financial conflicts of interest (FCOI) between pharmaceutical companies and physicians may negatively impact patient care. This is particularly relevant regarding clinical practice guidelines (CPG), where FCOI may inappropriately influence individual drugs’ promotion or use. In a cross-sectional analysis of pharmaceutical company payments, we sought to elucidate the extent of FCOI between Japanese hematologists and drug promotion in CPG. Data collected from two professional medical associations and companies belonging to the Japanese Pharmaceutical Manufacturers Association included the type and amount of company payments, individual financial disclosures, and new drug or indication approvals between 2015 and 2017. Of the 74 hematologists drafting CPG, 70 (94.6 %) received at least one payment during the study period. The cumulative median (interquartile range) value of these payments was $31,553 ($11,449-$74,390). Also, during this period, 26 new drugs or indications were approved and discussed in the CPG. Among the 79 pharmaceutical companies, the 11 (13.9 %) with newly approved and discussed drugs in the CPG made median (interquartile range) payments of $210,388 ($85,141-$292,536), while the remaining 68 (86.1 %) made $0 ($0-$9607) in payments. Disclosure of these payments was inconsistent. Such discrepancies suggest an association between pharmaceutical payments and drug approvals that only greater transparency can clarify. Consequently, a comprehensive overhaul of the current framework to control FCOI that includes legal regulation may be necessary.Copyright © 2020 Elsevier B.V. All rights reserved.