Childhood cancer is the number one cause of death by illness in children. However, despite being such a deadly disease, survival from childhood cancer is high with cancer treatment. Unfortunately, undergoing cancer treatment can result in many treatments related side-effects. Daily self-care such as maintaining a balanced diet, drinking enough fluids, practicing proper hygiene and getting enough rest, can be effective in lowering the severity of these symptoms. It is found that existing interventions for cancer patients do not target treatment adherence in children. Therefore, the aim of the research is to design an intervention which is able to motivate children to adhere to treatment and encourage daily self-care. To enhance the design of such an intervention, the article explores the potential of virtual pet games as a health intervention, and the use of the Protection Motivation Theory and Social Learning Theory’s observational learning in increasing the intervention’s effectiveness. Finally, the design considerations, game objectives and overall conceptual architecture of the proposed intervention are discussed. A conceptual comparison is also made between the proposed game and existing serious games for cancer patients. Future work is required to develop this design into a working prototype, and to evaluate its effectiveness on improving treatment adherence and promoting daily self-care with childhood cancer patients.