Abstract Background Cancer of Unknown Primary (CUP) is a metastatic cancer for which the primary lesion remains unidentifiable during life and little is also known about the modifiable risk factors that contribute to its development. This study investigates whether vegetables and fruits are associated with CUP risk. Methods We used data from the prospective Netherlands Cohort Study on Diet and Cancer which includes 120,852 participants aged between 55 and 69 years in 1986. All participants completed a self-administered questionnaire on cancer risk factors at baseline. Cancer follow-up was established through record linkage to the Netherlands Cancer Registry and the Dutch Pathology Registry. As a result, 867 incident CUP cases and 4005 subcohort members were available for case-cohort analyses after 20.3 years of follow-up. Multivariable adjusted hazard ratios were calculated using proportional hazards models. Results We observed no associations between total vegetable and fruit consumption (combined or as ...