The second near-infrared window （NIR-II， 900-1880 nm） overcomes critical limitations of visible （360-760 nm） and NIR-I （760-900 nm） imaging—including restricted penetration depth， low signal-to-background ratio， and tissue autofluorescence—establishing its pivotal role for in vivo deep-tissue bioimaging. With exponential growth in NIR-II photodiagnosis and phototherapy research over the past decade， bibliometric analysis is essential to map the evolving landscape and guide strategic priorities. We systematically analyzed 2，491 NIR-II-related publications （2009-2023） from the Web of Science Core Collection， employing scientometric tools for distinct analytical purposes： （a） VOSviewer， SCImago Graphica， and Gephi for co-authorship and co-occurrence network mapping； （b） the R bibliometrix package for tracking field evolution and identifying high-impact publications/journals. The search retrieved 2491 studies from 359 journals originating from 54 countries. The country with the most published articles is China. Chinese institutions drive >60% of publications， with Stanford University （USA） and Nanyang Technological University （Singapore） ranked as the top two institutions by research quality. International cooperation is becoming increasingly frequent. Fan Quli， Tang Benzhong and Dai Hongjie are the top 3 productive authors in this field. Keyword evolution identifies "photodynamic therapy" and "immunotherapy" as pivotal future directions. We summarize the most cited literatures and NIR-II imaging clinical trials. This study delineates the NIR-II research trajectory， highlighting China''s leadership， intensifying global collaboration， and interdisciplinary convergence. Future efforts should prioritize the novel NIR-II probe development for NIR-II imaging and clinical translation of photodynamic/immunotherapy combinational platforms.