The investigators propose to develop, implement, and evaluate a novel Colorectal (CRC) screening patient navigator program for patients with Mental Health (MH) and /or Substance Use Disorder (SUD) receiving care at Massachusetts General Hospital Charlestown. The study will involve randomly assigning eligible patients to early intervention or usual care/delayed intervention groups. The investigators believe this random assignment is ethical because Patient Navigation (PN) is an extremely limited resource, and all patients identified as eligible could not be contacted by the navigators in a short period of time. Thus the investigators will randomly assign access to PN during the study period, and then allow all patients to be navigated and screened after the study period is over. As a result, all eligible patients will be referred for PN, but the timing of the referral will be randomly assigned.