Background <p>A comprehensive assessment of the physical, psychological, social, and spiritual needs of cancer patients is crucial for holistic palliative care, yet a scientifically validated tool tailored for the Chinese population is lacking. This study aimed to develop and validate the Cancer Bio-psycho-social-spiritual Comprehensive Assessment Scale (CBCAS) for cancer patients across all disease stages.</p> Methods <p>The CBCAS was developed in three phases: (1) item generation based on a literature review and palliative care framework; (2) refinement through a two-round Delphi consultation with 15 experts; and (3) psychometric evaluation involving 400 cancer patients from two tertiary hospitals. We conducted item analysis, assessed content validity and internal consistency, and performed exploratory factor analysis (EFA).</p> Results <p>The final 54-item CBCAS encompasses nine factors identified via EFA, which collectively explain 60.00% of the total variance. Both item-level and scale-level content validity indices (I-CVI/S-CVI) reached 1.00. The scale demonstrated excellent internal consistency, with a Cronbach’s alpha of 0.91. </p> Conclusions <p>The CBCAS is a valid and reliable instrument for holistically assessing the bio-psycho-social-spiritual status of cancer patients in China. Its application can facilitate personalized care planning and early palliative interventions by providing a comprehensive understanding of patient needs.</p>