We have previously shown that 6 weeks of a diet containing epigallocatechin gallate (EGCG) and beta-alanine (B-ALA) was not effective in improving either cognitive or muscle function in aged (18 month) mice (Gibbons et al. Behav Brain Res 2014). However, diet reduced oxidative stress in the brain, and previous studies using longer-term interventions have documented beneficial effects in cognitive, but not muscle, function. Therefore, we investigated the effect of 6 months of feeding on measures of cognitive and muscle function in mice. Mice (12 months, N = 15/group) were fed AIN-93M containing 0.15% EGCG and 0.34% B-ALA or standard AIN-93M for 6 months, then underwent a battery of tests for cognitive and muscle function at 18 months. Interestingly, a higher percentage of mice receiving EGCG and B-ALA (E + B, 80%) survived to study end compared to control (Ctrl, 40%) mice (p = 0.02). E + B did not affect arm preference in the Y-maze test (p = 0.74, novel arm) and did not alter performance in an active avoidance test (p = 0.16, avoidances per 50 trials). E + B increased rotarod performance (p = 0.03), did not affect grip strength (p = 0.91), and decreased time to exhaustion in a treadmill fatigue test (p = 0.02) compared to Ctrl. In conclusion, E + B reduced mortality, had no effect on cognitive function and variable effects on muscle function.