Aging is accompanied by a decline in associative memory, whereas item memory remains relatively stable compared to young adults. This age-related associative deficit is well replicated, but its mechanisms and influencing factors during learning are still largely unclear. In the present study, we examined mediators of the age-related associative deficit, including encoding intentionality, strategy instructions, the timing of the memory test and the material being learned in a within-subject design. Older and younger adults performed seven encoding (...) tasks on word pairs and picture pairs on two consecutive days, followed by item and associative recognition tests. The associative deficit was evident after all encoding tasks. We found no evidence for a difference in the magnitude of the associative deficit between incidental vs. intentional learning conditions. However, there was some evidence for a larger associative memory deficit with pictures versus words when the encoding task was held equal. Sentence generation and interactive imagery instructions in which participants generated their own mediators reduced the magnitude of the associative deficit. However, increased encoding guidance through the provision of mediators did not lead to an alleviation of the deficit, potentially because the specified mediators were implausible or difficult for the older adults to reconcile with prior knowledge. Finally, we found some evidence for a reduced age-related associative deficit with a test delay of 24 h. These results contribute to a better understanding of the factors affecting the relative difficulty of older adults with encoding and retrieving novel associations. (shrink)