Exploratory behaviors are crucial to the adaptation of organisms to uncertain environments. Human neuroscience studies have implicated the intraparietal sulcus (IPS), anterior cingulate cortex (ACC), and medial prefrontal cortex (mPFC) in exploratory behaviors. However, the roles of these regions in signaling specific aspects of exploratory behaviors remain unclear. Based on earlier studies, we classified exploratory behaviors into two types driven by different motives: internal and external explorations. Internal exploration involves encountering options with uncertain outcomes and seeking information to reduce the uncertainty of these options. External exploration involves searching in the environment for new options. In the current study, we aimed to investigate the distinct neural mechanisms underlying internal and external explorations. We designed a decision-making task to unravel the roles of IPS, ACC, and mPFC in signaling exploratory decisions using fMRI. In the task, each trial began by revealing one option. Each option contained four possible points that could be earned by the participant. As such, an option was generally more rewarding when it contained more points and more uncertain when it contained more variable points. Participants were told to maximize their gain by deciding between three actions: 1) to end the trial by accepting an option and earn one of the possible points (i.e., reward collection), 2) to reduce the uncertainty of an option by randomly removing a set of points (i.e., internal exploration), and 3) to reveal a new option (i.e., external exploration). Each internal and external exploration would cost one point. We found distinct exploration signals in IPS and ACC that were linked to internal and external exploration, respectively. IPS guides internal exploration by monitoring the uncertainty of an option instead of the reward magnitude, whereas ACC signals the need to switch from internal to external exploration by tracking the value of new options. Signals in both regions were consistent regardless of the ensuing decision, emphasizing their roles in coding specific exploration values. Conversely, mPFC flexibly encodes the value of internal exploration, external exploration, or reward collection based on the decision being made. This suggests that mPFC signals general decision value, which aligns with the neural common currency hypothesis. Our research reveals the distinct roles of IPS and ACC in exploratory decision-making