This study aimed to present the content validity and reliability analyses of an instrument to study the determinant factors of salt consumption among hypertensive subjects, based on an extension of the Theory of Planned Behavior. Content validity was assessed by 3 experts and a pre-test was carried out with 5 subjects. The final tool, comprising 3 different behaviors related to salt consumption and corresponding psychosocial variables, was applied to 32 subjects for internal consistency and temporal stability (15-day interval) analysis. Cronbach's alpha coefficients > 0.70 and significant intra-class correlation coefficients were observed for most variables, indicating the temporal stability of the measured concepts. The developed instrument exhibited evidence of both content validity and reliability.