Interpersonal trust is a vital element in the social functioning of our relationships with persons, groups, and organizations. In the past two decades, an increase in task-based and task-free (resting-state) functional magnetic resonance imaging (fMRI) studies have been observed that explored the neuropsychological signatures of trust. In this book chapter, we compared the commonalities and differences between task-based fMRI (tb-fMRI) and task-free fMRI (tf-fMRI) approaches for studying trust and explored how these two approaches can make unique contributions to our understanding of the psychoneurobiological underpinnings of trust. Overlapping brain regions for both approaches have been identified in large-scale domain-general networks – reward (e.g., ventral striatum), salience (e.g., anterior insula), executive-control (i.e., lateral prefrontal cortex), and default-mode (i.e., temporoparietal junction) networks – supporting the underlying motivational, affective, and cognitive aspects of trust. While task-based research investigates dominantly those brain networks in building trust over time at the group level, task-free trust research has identified those networks in predicting trust preferences at the individual level. Future research would benefit from a combination of these two approaches for a broader understanding of the driving psychoneurobiological mechanisms of trust.