This study examined differential age effects in a young and a middle-aged sample by means of a sequential n-back task with increasing memory load. Participants processed two streams of stimuli either separately as a single task, or simultaneously as a dual task. We investigated age effects as a function of memory load in both the single and the dual-task version. In accuracy, we observed differential age effects as a function of load, which were more prominent in the dual-compared to the single-task versions. That is, middle-aged participants performed poorer than young adults in the dual-task conditions, suggesting that early age-related changes become especially apparent in conditions where task coordination and resource sharing come into play. Regarding latencies, we observed no differential age effect, which we believe is due to characteristics of the sequential n-back task.