Incorporating spouses into interventions for problematic alcohol use is associated with increased efficacy; yet, little is known about the therapeutic processes that may explain these effects. In a study of partner language use during couple‐focused alcohol interventions, we utilized a linguistic corpus comparison tool, Wmatrix, to identify semantic themes that differentiated couples with successful and unsuccessful treatment outcomes and may therefore also reflect potential change processes. Thirty‐three couples participated in a randomized control trial of Family Systems Therapy (FST) or Cognitive Behavioural Therapy (CBT). Linguistic comparisons of partners' speech during the therapy sessions suggested that drinks and alcohol was a significant differentiating semantic theme. Specifically, patients and spouses in FST with successful outcomes used more language related to drinks and alcohol than patients and spouses in FST with unsuccessful outcomes. Post‐hoc analyses of context suggested that, in FST, successful spouses spoke less about the patient's drinking and more about alcohol in general (without reference to an individual) than unsuccessful spouses. Conversely, spouses in CBT with successful outcomes used less language related to drinks and alcohol than spouses in CBT with unsuccessful outcomes. In CBT, successful spouses spoke more about the patient's and couple's drinking and less about the spouse's and other people's drinking than unsuccessful spouses. Results emphasize the role of spouse behaviour—in this case indexed via language use—in alcohol treatment outcomes. Findings also suggest potentially distinct therapeutic processes in FST and CBT and highlight the utility of linguistic corpus comparison methods in couple‐focused intervention research. Copyright © 2016 John Wiley & Sons, Ltd. Key Practitioner Message Incorporating spouses into interventions for problematic alcohol use is associated with increased efficacy; yet, little is known about the specific therapeutic processes that may explain these effects. Findings from this study suggest that semantic themes such as drinks and alcohol in partner speech during therapy sessions differentiate successful and unsuccessful treatment outcomes among couples participating in two couple‐focused interventions for problematic alcohol use. In addition, the context in which partners used alcohol‐related language differed by intervention type and treatment outcome, which suggests potential therapeutic processes that are unique to the two interventions (Family Systems versus Cognitive Behavioural Therapy).