Life expectancy among young cancer survivors has increased in the last decades. Unfortunately, young cancer survivors might still experience mental and physical issues due to cancer treatment. Moreover, although physical activity is a valid tool for increasing social support and reducing the risk of obesity, sedentary behaviour is very common among young cancer survivors. Therefore, the current pilot study aims to estimate lack of social support impact on physical activity practice on mental health and quality of life. A sample of 69 Italian young cancer survivors (60% females) were included in the study and physical activity, anxiety, depression and quality of life were assessed by self‐reported questionnaires. The results showed that a lack of social support for exercising was connected to higher depressive symptoms, while no influence was detected on anxiety. Concerning quality of life, the analysis of variance model showed a significant effect of the lack of social support on physical mobility but not on self‐care, usual activities, pain and discomfort and general health. In conclusion, integrating physical activity in young cancer survivors' lifestyle, considering cancer‐related side effects, might enhance their mental health and quality of life by providing social support at the same time. Healthcare professionals should evaluate the feasibility and support adapted physical activity programmes for young cancer survivors, to reduce the risk of depression and obesity, among others.