Background: Personal payments from the pharmaceutical industry to US physicians are common and are associated with changes in physicians’ clinical practice and interpretation of clinical trial results. We assessed temporal trends in industry payments to oncologists, with particular emphasis on payments to authors of oncology clinical practice guideline and on payments related to immunotherapy drugs. Methods: We included US physicians with active National Plan and Provider Enumeration System records and demographic data available in the Centers for Medicare & Medicaid Services Physician Compare system who had a specialty type of medical oncology or general internal medicine. Medical oncologists serving on NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) Panels were identified manually. Industry payments, and the subset associated with PD-1/PD-L1 drugs, were identified in Open Payments, the federal repository of all transactions of financial value from industry to physicians and teaching hospitals, from 2014 to 2017. Results: There were 13,087 medical oncologists and 85,640 internists who received payments. The mean, annual, per-physician value of payments to oncologists increased from $3,811 in 2014 to $5,854 in 2017, and from $444 to $450 for internists; the median payment increased from $152 to $199 for oncologists and remained at $0 for internists. Oncologists who served on NCCN Guidelines Panels received a greater value in payments and experienced a greater relative increase: mean payments increased from $10,820 in 2014 to $18,977 in 2017, and median payments increased from $500 to $1,366. Among companies marketing PD-1/PD-L1 drugs, mean annual per-oncologist payments associated with PD-1/PD-L1 drugs increased from $28 to $773. Total per-oncologist payments from companies marketing PD-1/PD-L1 drugs experienced a 165% increase from 2014 to 2017, compared with a 31% increase among similar companies not marketing PD-1/PD-L1 drugs. Conclusions: Pharmaceutical industry payments increased for US oncologists from 2014 to 2017 more than for general internists. The increase was greater among oncologists contributing to clinical practice guidelines and among pharmaceutical companies marketing PD-1/PD-L1 drugs. The increasing flow of money from industry to US oncologists supports ongoing concern regarding commercial interests in guideline development and clinical decision-making.