To explore influences on post-diagnosis dietary decision-making in colorectal cancer survivors (CRC) for future intervention development.Individual semi-structured interviews were conducted with 30 CRC survivors. All interviews were recorded and transcribed verbatim for grounded theory analysis.Most CRC survivors interviewed reported making both short- and long-term changes post-diagnosis, influenced by physical symptoms and personal beliefs: short-term treatment-driven changes to facilitate recovery, manage treatment side-effects and avoid disruption in treatment; short-term 'patient role' driven changes heavily influenced by family members and cultural beliefs; long-term changes driven by residual symptoms and illness beliefs, including cancer causal attributions and beliefs about preventing future recurrences. Traditional Chinese medicinal (TCM) beliefs were influential in both short- and long-term dietary decision-making, which may explain why survivors focused on specific food items rather than food patterns.While our findings suggested that the majority of CRC survivors made dietary changes post-diagnosis, their dietary pattern and motivation may change over the course of their illness trajectory. Also, the types of changes made are often not consistent with existing dietary recommendations. It is necessary to consider illness perception and cultural beliefs when delivering dietary care or developing interventions for this population.