The alarming prevalence of adult obesity warrants consideration of treatments with broad reach; digital health interventions meet this need and have demonstrated efficacy for weight loss. One approach that can be delivered remotely is motivational interviewing - a counseling style that helps resolve ambivalence to change unhealthy behavior. This is the first review to systematically examine eHealth and telehealth interventions that incorporate motivational interviewing for weight loss. We searched four electronic databases (PubMed, Embase, PsycInfo, CINAHL) for publications from November 2009-May 2018. Included papers were weight loss RCTs conducted among adults with overweight or obesity that examined eHealth or telehealth interventions with motivational interviewing, compared to any type of treatment arm without it. Results were presented separately by comparison arm (control vs. active comparator). Sixteen papers (15 trials) were included. Twelve used telephone-based counseling to deliver motivational interviewing, two used email and phone, and one used online chats. When compared to a no-treatment control arm, the motivational interviewing arm was associated with greater weight loss on 6 of 11 occasions, but performed better than an active comparator on only 1 of 7 occasions. Retention and engagement were generally high, though few trials examined the relation with weight loss. No trial had high risk of bias, but five lacked power calculations and only two reported fidelity to motivational interviewing. Telephone-based interventions that incorporate motivational interviewing hold promise as effective obesity treatments. There is a dearth of evidence to support the use of motivational interviewing via eHealth, signaling a needed research area.