This case report concerns a woman with intellectual disability, schizoaffective disorder, and avoidance and refusal of having her blood drawn. She required but refused blood draws to properly monitor the therapeutic dose of a necessary psychotropic medication. During intervention at a community-based habilitation setting and under simulated conditions, direct-care and supervisory staff (a) gradually exposed her to steps constituting a blood draw, (b) reinforced completed steps (praise and tokens), and (c) offered a monetary incentive to participate in an actual blood draw. Evaluated in a changing criterion design, the woman demonstrated increased compliance and eventually completed blood draws immediately following intervention, months later, and at 12- to 24-month follow-ups. We discuss implications from the case and the advantages of in vivo intervention for overcoming medical fears among people who have intellectual disability.