The term third-wave cognitive behavioral therapy (CBT) encompasses new forms of CBT that both extend and innovate within CBT. Most third-wave therapies have been subject to randomized controlled trials (RCTs) focused on clinical effectiveness; however, the number and quality of economic evaluations in these RCTs has been unknown and may be few. Evidence about efficiency of these therapies may help support decisions on efficient allocation of resources in health policies. The main aim of this study was to systematically review the economic impact of third-wave therapies in the treatment of patients with physical or mental conditions. We conducted a systematic literature search in PubMed, PsycINFO, EMBASE, and CINALH to identify economic evaluations of third-wave therapies. Quality and Risk of Bias (RoB) assessment of economic evaluations was also made using the Drummond 35-item checklist and the Cochrane Collaboration's tool for assessing risk of bias, respectively. Eleven RCTs were included in this systematic review. Mindfulness-Based Cognitive Therapy (MBCT), Mindfulness-Based Stress Reduction (MBSR), Acceptance and Commitment Therapy (ACT), Dialectical Behavior Therapy (DBT), and extended Behaviour Activation (eBA) showed acceptable cost-effectiveness and cost-utility ratios. No study employed a time horizon of more than 3 years. Quality and RoB assessments highlight some limitations that temper the findings. There is some evidence that MBCT, MBSR, ACT, DBT, and eBA are efficient from a societal or a third-party payer perspective. No economic analysis was found for many third-wave therapies. Therefore, more economic evaluations with high methodological quality are needed.