Human rights are rights of the humans by virtue of their being human beings. They are the basic rights which are equally guaranteed to the persons behind bars. Studies indicate the condition of prisons in India and the worsening physical & mental health of the prisoners. The prisons are heavily overcrowded with minimum facilities and limited medical infrastructure. This adds to the plight of prisoners who are mostly poor, jobless, neglected by family and community. Thus, they develop mental illness over time which mostly is diagnosed when the symptoms become noticeable. Mental health of both the under trial and convicted prisoners pose a major challenge for the government and the judiciary when it comes to interpretation before courts. The term “mental illness” is defined under the Mental Health Care Act 2017 which covers within its ambit different conditions of mental illness. The researcher through this paper highlights the causes of mental illness, the legislations, judicial approach and also mentions some of the suggestive measures which should be adopted for the mentally ill prisoners.