Brief motivational interventions (BMIs) are widely used and efficacious interventions that address alcohol misuse in mandated college students. Consistent with motivational interviewing (MI; Miller & Rollnick, 2013) theory, within-therapist improvements in MI-consistent (MICO) skills over time-that is, as a therapist gains skill through repeated practice-may be associated with concurrent increases in client change language and subsequent changes in behavior. This study examined how therapist skill changed over time and whether within-therapist improvement in MICO skills impacted in-session client change language and subsequent alcohol-related outcomes. BMI sessions (N = 228) from 2 randomized clinical trials that had led to significant reductions in alcohol use and alcohol-related problems in mandated student drinkers were coded using the Motivational Interviewing Skills Code 2.0 (Miller, Moyers, Ernst, & Amrhein, 2003). In both studies, the BMI consisted of a single 45- to 60-min session. Analyses examined session-by-session changes in therapist MICO skills, client change language, and alcohol use outcomes. Therapist MICO skills improved over time, and there were significant increases in client change language and decreases in client discussion of topics other than personal alcohol use. Among relatively heavy-drinking clients, those treated by a more experienced therapist demonstrated greater reductions in alcohol use; however, this association was not mediated by client change language. Increased experience conducting BMIs improved therapist MICO skills over time, which in turn increased the focus on personal alcohol use during the session. However, it remains unclear how client language predicts behavior change following a BMI. (PsycINFO Database Record (c) 2019 APA, all rights reserved).