In the field of psychotherapy, scientific research has highlighted the importance of empathy and therapeutic alliance in regard to the effectiveness and better results of psychological treatments. In recent years, mindfulness-based interventions (MBIs) have shown to be effective at increasing empathy and therapeutic alliance and how this could affect the patients’ symptomatology. In this study, we conducted a systematic review of the effectiveness of MBIs applied to psychotherapists to increase their self-perceived empathy, therapeutic alliance reported by them and their patients, and the effects perceived by patients on their symptomatology. Sixteen efficacy studies evaluating the impact of an MBI on some of these variables were identified, of which six included measures evaluated by the patients whose therapists received the MBI. The risk of bias of the included studies was analyzed following the methodological standards. We found very different designs and methodologies in the studies included in this review, with few of them including a control group. The results show a limited increase in empathy, measured by the psychotherapist, after an MBI. However, the results in therapeutic alliance are not conclusive, as well as the improvements in the perception of patients toward their symptomatology. It is concluded that MBIs can have a beneficial effect on the psychotherapeutic practice, through the development of psychotherapists’ empathy. Future research would require new studies with a higher methodological quality, in addition to new studies that analyze the effects of MBIs on empathy, therapeutic alliance and patient symptomatology, and the possible relationships between them.