BACKGROUND AND AIMS: Physical activity and nutritional supplementation interventions may be used to ameliorate age-related loss of skeletal muscle mass and function. Previous reviews have demonstrated the beneficial effects of resistance exercise training (RET) combined with protein or essential amino acids (EAA) in younger populations. Whether or not older adults also benefit is unclear. The aim of this review was to determine whether regular dietary supplementation with protein/EAA during a RET regimen augments the effects of RET on skeletal muscle in older adults. METHODS: A literature search was conducted in August 2015 using MEDLINE, EMBASE, SPORTDiscus, and CINAHL Plus to identify all controlled trials using a RET regimen with and without protein/EAA supplementation. Outcome variables included muscle strength, muscle size, functional ability, and body composition. RESULTS: Fifteen studies fulfilled the eligibility criteria, including 917 participants with a mean age of 77.4 years. Studies involving both healthy participants and those described as frail or sarcopenic were included. Overall, results indicated that protein supplementation did not significantly augment the effects of RET on any of the specified outcomes. Exceptions included some measures of muscle strength (3 studies) and body composition (2 studies). Meta-analyses were conducted but were limited because of methodologic differences between studies, and results were inconclusive. CONCLUSIONS: Systematic review and meta-analysis of controlled trials reveal that protein/EAA supplementation does not significantly augment the effects of progressive RET in older adults.