Self-regulation consumes a form of strength or energy. The authors investigated aftereffects of self-regulation depletion on muscle-endurance performance in older adults. Participants (N = 61, mean age = 71) were randomized to a self-regulation-depletion or control group and completed 2 muscle-endurance performance tasks involving isometric handgrip squeezing that were separated by a cognitive-depletion task. The depletion group showed greater deterioration of muscle-endurance performance than controls, F(1, 59) = 7.31, p = .009. Results are comparable to those of younger adults in a similar study and support Baumeister et al.'s limited-strength model. Self-regulation may contribute to central-nervous-system fatigue; however, biological processes may allow aging muscle to offset depletion of self-regulatory resources affecting muscle-endurance performance.