Prehabilitation aims to improve post-operative outcomes by enhancing pre-operative fitness but is labour-intensive. This pilot study aimed to assess the efficacy of a tri-modal prehabilitation programme delivered by smartwatches for improving functional fitness prior to major abdominal cancer surgery. A single-centre, randomised controlled pilot study, in which 22 patients were randomised to: (a) a prehabilitation group (n = 11), comprising of home-based exercise, nutritional, and dietary advice delivered using a wrist-worn smartwatch connected to a smartphone application; or (b) a control group (n = 11) receiving usual care, with patients given a smartwatch as a placebo. Eligible participants had over two weeks until planned surgery. The primary outcome was pre-operative physical activity including 6-min walk test (6MWT) distance, with secondary outcomes including change in body weight and hospital anxiety and depression score (HADS). Recruitment was 67% of eligible patients, with groups matched for baseline characteristics. The prehabilitation group engaged in more daily minutes of moderate [25.1 min (95% CI 9.79-40.44) vs 13.1 min (95% CI 5.97-20.31), p = 0.063] and vigorous physical activity [36.1 min (95% CI 21.24-50.90) vs 17.5 min (95% CI 5.18-29.73), p = 0.022] compared to controls. They also had significantly greater improvements in 6MWT distance compared to controls [+ 85.6 m (95% CI, + 18.06 to + 153.21) vs + 13.23 m (95% CI - 6.78 to 33.23), p = 0.014]. HADS scores remained unchanged from baseline in both groups. Prehabilitation in the colorectal cancer care setting can be delivered using smartwatches and mobile applications. Furthermore, this study provides early indicative evidence that such technologies can improve functional capacity prior to surgery TRIAL REGISTRATION: NCT04047524.