During the last two decades a number of therapies, under the name of the third wave of cognitive behavior therapy (CBT), have been developed: acceptance and commitment therapy (ACT), dialectical behavior therapy (DBT), cognitive behavioral analysis system of psychotherapy (CBASP), functional analytic psychotherapy (FAP), and integrative behavioral couple therapy (IBCT). The purposes of this review article of third wave treatment RCTs were: (1) to describe and review them methodologically, (2) to meta-analytically assess their efficacy, and (3) to evaluate if they currently fulfil the criteria for empirically supported treatments. There are 13 RCTs both in ACT and DBT, 1 in CBASP, 2 in IBCT, and none in FAP. The conclusions that can be drawn are that the third wave treatment RCTs used a research methodology that was significantly less stringent than CBT studies; that the mean effect size was moderate for both ACT and DBT, and that none of the third wave therapies fulfilled the criteria for empirically supported treatments. The article ends with suggestions on how to improve future RCTs to increase the possibility of them becoming empirically supported treatments.