BACKGROUND Motivation to change substance use behavior is an important component of the recovery process that has usually been studied at entry into treatment. Less studied, but equally important, is the measurement of motivation over time and the role motivation plays in subsequent substance use. OBJECTIVE The present study sought to examine longitudinal motivation toward sobriety among residents of sober living houses. METHODS Sober living residents (n = 167) were followed at 6-month intervals over an 18-month period and assessed for motivation and substance use outcomes at each study interview. Motivation was measured using the costs and benefits subscales of the Alcohol and Drug Consequences Questionnaire (ADCQ) and substance use outcomes included the Addiction Severity Index (ASI) alcohol scale, ASI drug scale, and peak density of substance use (number of days of most use in a month). RESULTS Participants reported higher benefits than costs of sobriety or cutting down substance use at every study time point. Using lagged generalized estimating equation models, the ADCQ costs predicted increased severity for alcohol, drugs, and peak density, whereas the benefits subscale predicted decreased drug and peak density. CONCLUSIONS Longitudinal measurement of motivation can be a useful clinical tool to understand later substance use problems. CONCLUSIONS Given the mixed findings from prior studies on the effects of baseline motivation, a shift toward examining longitudinal measures of motivation at proximal and temporal intervals is indicated.