Introduction: Physical activity and cardiorespiratory fitness (CRF) are protective factors in cancer development. However, the CRF in the Chilean population diagnosed with cancer is unknown. This study aimed to evaluate the association that the CRF had between people with and without a cancer diagnosis and, secondarily, to compare the trend of the CRF according to years of cancer diagnosis in the Chilean population. Methods: Data from 5,483 people from the 2016-2017 National Health Survey between 15 and 98 years old were analyzed. Cancer diagnosis (all available) was determined with standardized questions, and CRF was calculated with an abbreviated method (demographics, anthropometry, lifestyles). Linear regression analysis adjusted for confounding variables was performed with the complex sample analysis module of the STATA v.16 program (95% CI, p < 0.05). Results: People with some cancer diagnosis versus those without cancer had a lower FCR level (β: -1.23 [95% CI: -1.52; -0.94]). When comparing CRF levels according to cancer type, similar results were observed for colorectal, breast, and uterine cancer (p < 0.001) but not for thyroid cancer (p = 0.253). There was lower CRF from the first year of diagnosis of all types of cancer to over ten years, although not significant (p = 0.109). Conclusions: Those diagnosed with cancer presented lower CRF compared to those not diagnosed. In addition, in people with cancer, the CRF decreased with increasing years since the first diagnosis. It would be essential to evaluate and increase CRF in cancer patients.