Among all pediatric hematologist-oncologists (PHOs) certificated by the Japanese Society of Pediatric Hematology/Oncology (JSPHO), 215 PHOs (70.0%) received $908,900 personal payments from 54 pharmaceutical companies between 2016 and 2019. Four-year combined average payments per author was $2,961 (standard deviation: $6,299). While the prevalence of physicians with payments was relatively stable during the study period with 40.4% and 44.6% in 2016 and 2019, the average annual personal payments increased nearly double from $559 in 2016 to $1,096 in 2019, respectively. Payments from the top five companies with the largest total payments accounted for 48.8% of total monetary values.