Working memory (WM) represents the capacity to store and process a limited amount of information. Better understanding developmental changes of WM forms a key topic in research on neuropsychology of aging. Previous studies reveal age-differences in WM and in executive functions (EFs). Although EFs are seen as essential mechanisms in WM, the specific relation between the two cognitive constructs so far remains unclear. The present study set out to investigate the unique roles of the three main facets of EFs (i.e., updating, inhibition, and shifting) in accounting for age-related variability in WM. Therefore, one-hundred seventy-five younger and 107 older adults performed a battery of cognitive tests including measures of WM, EFs, and processing speed. A set of statistical approaches including regression analyses and path models was used to examine the cognitive correlates that could explain individual and age-related variance in WM. Significant age-differences were found on WM and on EF measures. Regression analyses and path models showed that updating and inhibition but not shifting played a major role in explaining age-related variance in WM. In sum, findings suggest that updating and inhibition are most influential for age-differences in WM. They further show that age and processing speed do not significantly contribute to variability in WM performance beyond executive resource. The present findings have implications for conceptual and developmental theories of WM and may further offer an initial empirical basis for developing possible trainings to improve older adults’ WM performance by strengthening the efficiency of updating and inhibitory processes.