While data and information exchanges theoretically play an effective role in the decision-making process of a shared watercourse, in practice, there are several challenges that prevent riparians from sharing data in an effective and cooperative manner. This chapter seeks to assess why the riparian nations of the Helmand River have failed to adopt an effective data exchange mechanism although both nations signed an internationally recognized bilateral water treaty in 1973. Applying a mixed study approach, the study draws on the theory of planned behavior (TPB) to interpret the main obstacles of data sharing between Afghanistan, the upstream state, and Iran, the downstream state, of the Helmand River Basin. Using both secondary literature data and stakeholder interviews, this research found a number of specific factors that impede the ability of the riparian nations of the Helmand River to share data and information, such as national security, political instability, lack of capacity, negative emotions, pride, and historical factors. Our research suggests that these underlying elements have been under-estimated in the TPB models of data sharing at the transboundary level. Thus, borrowing from Wehn’s model (2003b), we have developed a modified version of TPB to unpack the challenges of data sharing between the riparian states of the Helmand River Basin.