Abstract: BACKGROUND: Effort-based decision-making (EBDM) is a key component of motivation. Impairments in EBDM have been consistently linked to amotivation in individuals with schizophrenia (SZ). Similar deficits are seen in SZ and bipolar disorder (BD), despite striking differences in motivational profiles between the two disorders. Similar task behavior, but distinct motivational profiles, may arise from functional differences in brain regions supporting EBDM. METHODS: 28 Veterans with SZ, 21 with BD, and 30 controls completed a cognitive EBDM task during fMRI scanning. Participants chose between an easy and a more effortful working memory task. Reward values were manipulated to bias the participant toward choosing the more effortful task, the easier task, or were relatively unbiased. RESULTS: Participants with SZ spent less time deliberating on unbiased trials and exhibited reduced task-related activation in the ACC, anterior insula, and dlPFC compared with control and BD groups. Greater activation to hard-task biased trials relative to unbiased or biased toward easy task trials in the striatum, vmPFC, and PCC was associated with motivation deficits in SZ, but lower amotivation in BD. CONCLUSIONS: Hypoactivation to the task in the ACC and other regions was found in the SZ group. Associations found between activation in several brain regions underlying EBDM and clinical amotivation suggest distinct neurobehavioral processes contributing to motivational deficits in SZ and BD.