Purpose <p>Understanding patients’ opinions and beliefs regarding how to support an active life and decrease sedentary behavior (SB) during treatment is necessary to inform effective interventions for reduced SB. Therefore, the purpose was to explore the opinions and beliefs of patients receiving neo- or adjuvant cancer treatment on how to support the decrease in SB and how to replace sedentary time.</p> Methods <p>A purposive sample of patients receiving neo- or adjuvant cancer treatment for breast (<i>n</i> = 10), prostate (<i>n</i> = 5), or colorectal cancer (<i>n</i> = 7) partook in five focus group interviews. Transcripts from the interviews were analyzed with a thematic analysis.</p> Results <p>Three themes were identified in the analysis: participants describe that the decrease of SB and replacing time in sedentary behavior can be supported by <i>Healthcare and employer engagement</i>, <i>Socialization</i>, and lastly by <i>Self-help</i>. For instance, early information and encouragement from healthcare personnel, adaptations at work, support from relatives and peers, as well as finding routines and setting goals were considered important for reducing SB. Focusing on daily activities and joyful activities were examples of ways to replace sedentary time.</p> Conclusions <p>Interventions for reducing SB may benefit from addressing several aspects from the patient’s life and focusing on replacing SB with daily activities and not only on health-enhancing physical activity. Healthcare staff should provide early information and continuous encouragement for patients about reducing sedentary behavior during oncological treatment. Collaboration with patients to identify and implement practical strategies such as support from family and friends, workplace adaptations, and goal setting may be helpful.</p>