Background: Hyperprogressive disease is an unexpected response pattern observed in immune checkpoint therapy and associated with poor prognosis. The rechallenge of programmed cell death 1/programmed cell death ligand 1 (PD-1/PD-L1) inhibitors can be a treatment option in non-small cell lung cancer (NSCLC) patients who once responded to them. Here, we reported the hyperprogressive phenomenon after PD-1/PD-L1 rechallenge in a patient with NSCLC., Case Description: This case report described a patient with recurrent large cell lung cancer undergoing hyperprogressive disease with pleural and pericardial dissemination shortly after the pembrolizumab rechallenge, although he had a favorable response to the initial pembrolizumab treatment. A lower ratio of CD8 + T cells to Foxp3 + regulatory T cells was distributed in the cell blocks of pleural and pericardial effusion which were taken after hyperprogressive disease, compared to the resected tumor microenvironment. Neutrophil-to-lymphocyte ratio (NLR) was lower in peripheral blood when the disease was controlled and it rose when the disease progressed. Notably, NLR increased dramatically when hyperprogression occurred., Conclusions: For the first time, we reported that a patient who showed a favorable response to initial anti-PD-1 treatment underwent hyperprogressive disease when rechallenging the same immunotherapy. The increased Foxp3 + regulatory T cells in the tumor microenvironment and the longitudinal change of NLRs in peripheral blood were suggested to be associated with hyperprogressive disease., Competing Interests: Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://tlcr.amegroups.com/article/view/10.21037/tlcr-23-765/coif). T.S. received grants from AstraZeneca, Chugai Pharmaceutical, Boehringer Ingelheim, Novartis, MSD and received payment or honoraria for lectures, presentations, speaker bureaus from AstraZeneca, Chugai Pharmaceutical, Boehringer Ingelheim, Novartis, MSD, Taiho Pharma, Daiichi-Sankyo, Ono Pharmaceutical, Bristol-Myers Squibb, Nippon Kayaku, Pfizer, Takeda, Eli Lilly and Company, AMGEN; outside of this work. K.S. received payment or honoraria for lectures, presentations, speaker bureau from Ethicon and Intuitive. S.K. received grants from Ono Pharmaceutical, Eisai, Boehringer Ingelheim, Astellas Pharma, Daiichi Sankyo, Takara Bio, MSD Chugai, Pfizer, Astra Zeneca, Incyte, Abbvie, Takeda, GSK, LOXO/Lilly and consulting fees from Ono Pharmaceutical, Chugai, Astra Zeneca, Sumitomo Pharma, GSK, Rakuten Medical, ImmuniT Research, United Immunity, Astellas Pharma. SK received lecture fee from Ono Pharmaceutical, Bristol-Myers Squibb, Astra Zeneca, Chugai, MSD, Merck KGaA; outside of this work. K.T. received grants from Chugai Pharmaceutical Co., Ltd., Nippon Boehringer Ingelheim Co., Ltd., NIPPON SHINYAKU Co., Ltd., TSUMURA & Co., Pfizer Inc, TAIHO, PHARMACEUTICAL Co., Ltd., KYORIN Pharmaceutical Co., Ltd., TEIJIN PHARMA LIMITED, Sanofi K. K., ONO PHARMACEUTICAL Co., Ltd., Novartis Pharma K. K, SHIONOGI & Co., Ltd., Eli Lilly Japan K. K., Bayer Yakuhin, Ltd, DAIICHI SANKYO Co., Ltd., NIPRO PHARMA CORPORATION, Asahi Kasei Pharma Corporation, Nippon Kayaku Co., Ltd., Takeda, Pharmaceutical Company Limited, Kyowa Kirin Co., Ltd., and honoraria for speaking at sponsored meetings including Chugai Pharmaceutical Co., Ltd., Nippon Boehringer Ingelheim Co., Ltd., MSD K. K, Pfizer Inc, AstraZeneca K. K, TAIHO PHARMACEUTICAL Co., Ltd., KYORIN Pharmaceutical Co., Ltd., Merck Biopharma Co., Ltd., ONO PHARMACEUTICAL Co., Ltd., Nippon Kayaku Co., Ltd., Novartis Pharma K. K, Eli Lilly Japan K. K, Sumitomo Dainippon Pharma Co., Ltd., Bristol-Myers K. K, Meiji Seika Pharma Co, Ltd., Takeda Pharmaceutical Company Limited, Viatris Inc, Janssen Pharmaceutical K.K, Abbott Japan LLC, Thermo Fisher Scientific Inc. K.T. obtains patents “METHOD FOR DETECTING CELLS” (issued), “THE METHOD FOR DETECTING CIRCULATING TUMOR CELLS USING VIRUS” (pending), and “CALML5 is a novel diagnostic marker for differentiating thymic squamous cell carcinoma from type B3 thymoma” (pending). K.T. serves as Board of Director in The Japan Lung Cancer Society and The Japanese Respiratory Society. The other authors have no conflicts of interest to declare., (2024 Translational Lung Cancer Research. All rights reserved.)