The population of incarcerated older adults is the fastest growing demographic in prisons. Older persons in custody have poorer health as compared with those in the community. The unmet and complex health care needs of incarcerated older adults with mental illness raise justice, safety, dignity and fairness in care as ethical concerns. As there exists research gap to better understand these concerns, the current study aimed at exploring the perspectives of mental health professionals on challenges in delivering ethically competent care to mentally ill incarcerated older adults in Canada.; Thirty-four semi-structured interviews were conducted between August 2017 and November 2018 with prison mental health professionals in Canada who were selected using purposive and convenience sampling techniques. The audio recorded interviews were transcribed verbatim and analysed inductively to generate themes.; The results were distilled into three main categories and seven subcategories that related to ethical issues in the provision of health care for mentally ill incarcerated older adults. The main categories included imprisoned older persons with special care needs, lack of resources, and the peer-support program.; Results of this study showed that existing practices of care of mentally ill incarcerated older adults are characterised by challenges that increase their vulnerability to worse health conditions. It is imperative for local authorities, policy makers and representatives to prepare for and respond to the challenges that compromise ethically competent health care for, and healthy ageing of, mentally ill incarcerated older adults.