The goal of the present study was to identify the dimensions present in items representing internal barriers to substance abuse treatment and to test their invariance across gender, ethnic, and age groups. Twenty items from the Barriers to Treatment Inventory (BTI) were used to assess the structure and nature of the internal treatment barriers of 518 clients presenting to a central intake unit for a substance abuse assessment. Exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) revealed that a five factor model provided the best fit to the data. Internal treatment barriers were best described by five dimensions: absence of problem, negative social support, fear of treatment, privacy concerns, and committed lifestyle. Extending the confirmatory factor analysis to test multi-group invariance, there were some differences in measurement and structural relations among the internal barrier dimensions across gender, ethnic, and age groups. However, the lack of invariance was small and practically insubstantial. The findings led to the conclusion that the theoretical constructs measured by the five internal barrier dimensions are equivalent across important characteristics in this population.