Blonigen DM, et al. - In view of prior work suggesting changes in personality traits during substance use disorder (SUD) treatment, researchers here examined US military veterans ( n = 200) enrolled in SUD residential treatment with the aim to determine whether changes in the personality factors of positive emotionality (PEM), negative emotionality (NEM), and constraint (CON) during treatment associate with subsequent changes in abstinence self-efficacy and SUD symptoms. Using univariate and bivariate latent change score models, data were analyzed at treatment entry, discharge, and 12-months postdischarge. During treatment, there was an increase in PEM, CON, and abstinence self-efficacy, while NEM reduced, on average. Posttreatment, change in negative emotionality and constraint are sustained. Change in constraint during-treatment was predictive of posttreatment change in self-efficacy. Findings overall suggest a possible correlation of personality changes, marked by improvements in impulse control over the course of SUD treatment, with subsequent improvements in treatment outcomes and its possible value as a proximal treatment target among SUD patients during residential care.