A growing number of studies have shown that, compared to young adults, older adults better remember positive information than negative information. However, it is not clear whether this age-related positivity effect relies on an increase in positive information memory and/or on a decrease in negative information memory. Thus, we aimed to study the specific mechanisms underlying the age-related positivity effect in different memory tasks. To do so, we used an emotional word memory paradigm including immediate free recall, recognition and delayed free recall tasks. Forty-five young adults (m = 20.0 years) and 45 older adults (m = 69.2 years) native French speakers participated. Thirty-six low French words, including 12 negative (e.g. égout), 12 positive (e.g. lagune) and 12 neutral (e.g. notion) words were selected from an emotional lexical database (Gobin et al. 2017). For the recognition task, 36 new words were selected. The results showed that the age-related positivity effect specifically depended on a decrease in negativity preference (i.e. the comparison between negative and neutral words) in older adults, in comparison with young adults, both in immediate and delayed free recall tasks. Indeed, in these tasks, young adults recalled more negative than neutral words whereas there was no difference in older adults. In recognition task, no age-related positivity effect has been observed. Moreover, the results showed that, in immediate recall, the higher the older adults memory abilities, the lower their negativity preference. This correlation was not significant in delayed recall. These results suggest that, when compared with young adults, older adults disengage from negative words processing through costly cognitive processes. A small magnitude of negativity preference would indicate good maintenance of memory abilities. Results are discussed in the framework of the socioemotional selectivity theory.