Objectives Mindfulness training (MT) has emerged as a promising tool to promote cognitive functioning and psychological health. As a result, demand for scalable dissemination of MT is increasing across many time-pressured settings. One such setting is the military family. Military spouses face numerous challenges and yet there is a paucity of evidence-based training programs available that are tailored to promote their cognitive functioning and psychological health. Methods In the present study, we examined the impact of a 4-week MT program contextualized for military spouses and delivered via a peer train-the-trainer approach by fellow military spouse instructors (SIs). SIs first participated in an MT teaching practicum to learn how to deliver the program. They then delivered the MT program to military spouse participants (MT group, n = 48). The MT group was tested before (T1) and after (T2) the training interval and compared to a no-training control group (NTC group, n = 58) that did not receive MT but completed both testing sessions. Results Compared to the NTC group, the MT group showed benefits on measures of cognitive abilities, psychological health, and well-being. Particularly, benefits were reflected in the decrease over time (T1 to T2) in daily cognitive failures and depressive symptoms. Furthermore, correlation analyses revealed that greater MT practice corresponded with greater improvements in objective attentional performance. Conclusions These findings provide initial evidence for the beneficial effects of a tailored MT program when delivered by peer trainers. Trial Registration Clinicaltrials.gov (NTC03308344).