The purpose of the present study was to examine the nature of the relationships among dispositional optimism/pessimism, self-efficacy, and physical function in a cross-sectional sample of older women (N = 249, M age = 69 years). Initial bivariate analyses indicated that both pessimism and self-efficacy, but not optimism, were significantly correlated with objectively measured physical function. Subsequent analyses using covariance modeling with the full-information maximum likelihood estimator indicated that pessimism was no longer correlated with function when controlling for self-efficacy. That is, consistent with a social cognitive perspective, controlling for self-efficacy attenuated the relationship between pessimism and function. Our findings provide support for using a social cognitive perspective to understanding dispositional and modifiable influences on declines in function associated with aging.