In this article we describe and illustrate various visual and nonparametric techniques that can be used to evaluate the effectiveness of interventions in single-case experiments. Using an alternating treatments design across 2 cases, we tested whether practicing mindfulness would help a novice therapist stay focused and respond to a client more empathically and genuinely. Specifically, after taking a brief workshop on mindfulness, one male and one female doctoral trainee were asked, immediately before beginning each of 10 sessions, either to engage in a guided mindfulness practice for three minutes or a control activity of their choice. Five experimental and 5 control sessions were randomly scheduled for each therapist. The clients were unaware of the purpose of the study and the nature of the experimental manipulation. After each session, we administered measures of client-rated empathy, client- and therapist-rated real relationship, and therapist-rated level of hindering self-awareness. The graphed data were examined separately for each measure. Results showed that the client in Dyad 1 perceived the therapist as more empathic following mindfulness sessions, and the therapist reported less hindering self-awareness and rated the real relationship more favorably, with moderate to strong experimental effects. By contrast, Dyad 2 showed moderate to strong experimental effects for mindfulness practice on ratings of the real relationship, but not on empathy or hindering self-awareness. A cross-case comparison illustrates how replicated single-case experimental research with self-report data can advance our understanding of individual differences in response to psychotherapeutic interventions. (PsycINFO Database Record (c) 2018 APA, all rights reserved).