Can a person with mental illness buy a critical illness plan?

It depends. Without further details on the medical condition, it is difficult to ascertain whether the person is insurable. Generally, it is possible to be insured and yes, I have worked with clients with pre-existing mental conditions.

I share quality content on estate planning and financial planning here.

Hi Di, it would depend on the type, severity, and if the assured is still being treated or have been discharged of Mental illness as well.

I have clients with anxiety disorders accepted with no loading and just exclusion to Total and Permanent Disability, and I have seen others outright rejected.

I would suggest doing a preliminary underwriting with as many insurers as possible with the latest medical report or doctor's memo you can get and see what underwriters say.