The present research aimed to develop and produce evidence of the validity of an Implicit Association Test (IAT) for BJW. Two studies were developed to achieve this objective. Study 1 tested the convergent validity of a preliminary version of an IAT with an explicit measure (Global Belief in Just World Scale). The sample consisted of 119 participants who took part via the internet. After adjustments of the preliminary version, two IATs were developed, one for the general dimension (G-IAT) and another for the personal dimension of BJW (P-IAT). Both implicit measures and the explicit BJW measure were applied to 139 participants in a study conducted online. Both IATs demonstrated satisfactory psychometric properties and only the G-IAT correlates with the GBJWS as hypothesized.