To counter age-related decline in cognitive abilities, interventions such as working memory trainings have shown some promising results in old age. Yet, findings are mixed and there is enormous interindividual variability in training and transfer effects. Thus, it is still an open question which person-specific factors may moderate training and transfer effects in working memory interventions in older adults. The present study investigated this issue in the context of an established verbal working memory training. Eighty-eight participants (age range 60–82 years) performed either four sessions of the Borella et al. ( Psychology and Aging 25 (4):767 – 778, 2010 ) working memory training or of a visual search training as active control condition or belonged to a passive control group. Before and after the training, partici- pants performed a test battery to assess different cognitive abilities and everyday competence. Furthermore, we included questionnaires on personality factors and intrinsic motivation as possible covariates. The training group showed a substan- tial training gain in the working memory criterion task that was not found in the active control group. Furthermore, only participants of the working memory training showed also near transfer to another working memory task. No far transfer ef- fects including everyday competence emerged. In terms of possible moderators, age and crystallized intelligence influ- enced the training and transfer gain in the training group. In conclusion, our results showed that working memory can be improved in older adults and improvements transfer to a non- trained working memory task. However, person-specific fac- tors have to be considered to understand who benefits from the training and why.