This document discusses, among other things, systems and methods to acclimate a patient to therapy from an implantable medical device. For instance, an implantable medical device can include pulse generation circuitry, sensing circuitry, and a controller. The pulse generation circuitry can generate electrical pulses. The sensing circuitry can be for sensing cardiac electrical activity of the patient. In an example, the controller can detect cardiac events that define pacing timing intervals and control the delivery of electrical pulses in accordance with a programmed mode. The controller can be programmed to provide instructions to the pulse generation circuitry to deliver electrical pulses to the heart of a patient. In an example, the electrical pulses can be based on a therapy parameter. The controller can be configured to adjust the therapy parameter according to an acclimation profile to acclimate the patient to a stimulation therapy.