Background: Prospection, which is closely related to negative symptoms in patients with schizophrenia, is mainly associated with the Default Mode Network (DMN). Although abnormalities of the DMN have been reported in schizophrenia patients and at-risk individuals, little is known about the relationship between functional connectivity of the DMN and prospection in these clinical and subclinical populations. Method: Study 1 recruited 40 schizophrenia patients and 29 healthy controls, while 31 individuals with social anhedonia (SocAhn) and 28 controls participated in Study 2. Participants in both studies were asked to complete a prospection task and underwent resting-state functional MRI scans. Eleven regions of interest (ROIs) in the DMN were defined. Functional connectivity between each ROI and whole brain voxels were calculated and compared between groups (schizophrenia vs. control and SocAhn vs. control). Correlation analysis was conducted between altered functional connectivity and prospection variables in the schizophrenia and SocAhn groups. Results: Schizophrenia patients showed both hyper-connectivity and hypo-connectivity at the medial temporal lobe (MTL) subsystem of the DMN. Decreased connectivity between the ventral medial prefrontal cortex (vMPFC) and the right superior temporal gyrus (rSTG) was correlated with poor thought/emotion details in prospection. In individuals with SocAhn, decreased connectivity between the retrosplenial cortex (Rsp), a region of the MTL subsystem, and the right fusiform gyrus, was found and this was correlated with their prospection performance. Conclusion: Altered functional connectivity of the key nodes of the MTL subsystem was found in both patients with schizophrenia and individuals with SocAhn. Moreover, hypo-connectivity of the vMPFC was found to be correlated with prospection impairments in schizophrenia patients.