PURPOSE: This article reports the results of a single-case experimental multiple-baseline study across participants aiming to evaluate treatment effects of a metacognitive, joint reflection intervention package for social communication after acquired brain injury (ABI). METHOD: Four adults with a history of ABI and their everyday communication partners (ECPs) participated in a novel intervention, the Collaborative Interpersonal Strategy Building with Audio Reflection (CISBAR), incorporating collaborative goal setting, metacognitive strategy instruction, and joint audio reflection. Primary participants and ECPs engaged in 6- to 7-min conversations on opinion topics during the baseline, intervention, and follow-up phases. Raters scored turn-taking behavior (interruption, length of speaking turn) in each videorecorded conversation sample in random order without knowing study phase. Pre-/post-intervention questionnaires captured client and partner perspectives of communication changes. RESULTS: All four participants achieved personal communication goals. Visual analysis of specific communication targets supported a treatment effect in the two participants targeting interruption, but not in the two participants targeting verbosity. Design-comparable effect size analysis showed a medium effect size for decreasing interruption. Communication skills of all participants improved following CISBAR according to self- and partner-report questionnaires. Improvements in communication target behaviors maintained at 1-month follow-up. CONCLUSIONS: Results suggest that CISBAR shows promise as a treatment package for improving social communication post-ABI. The discussion considers the complexities of measuring changes in social communication, the treatment ingredients and candidacy considerations for CISBAR, and the emphasis on shared decision making in the therapy process.