Age-related source monitoring decline in episodic memory has been traditionally attributed to executive dysfunctioning. However, the literature does not reveal whether all source monitoring categories are impaired at the same level in the elderly. It is also unclear whether the source monitoring decline can be attributed to a specific executive function. In the present paper, we address these shortcomings by using specific source monitoring and executive tasks. Twenty four young and 22 older healthy adults, paired by sex and vocabulatory level, were assessed with original and simple source monitoring tasks tapping reality monitoring (discrimination between self-vs. other-generated sources), external monitoring (discrimination between external sources), and internal monitoring (discrimination between self-generated sources). They were also given specific executive measures assessing inhibition, flexibility, and updating. Relatively to the younger adults, poor source monitoring was found in the older participants. This decline was more pronounced for external monitoring. The latter performance was further predicted by inhibition. Our results emphasize the role of inhibitory processes in older adults' source monitoring decline.