Formal classroom learning is a lifelong pursuit. Many older adults return to school to advance their careers, learn new skills, or simply for personal fulfillment. As such, methods for improving learning should be considered in relation to both younger and older learners in order to properly assess their ultimate usefulness. A technique that has been demonstrably effective at improving learning and memory in younger students is testing. Testing improves memory more than mere exposure to material (e.g., restudying), a benefit known as the positive testing effect. However, recognition tests, where learners are exposed to correct and incorrect information (e.g., multiple-choice tests), also introduce false information to test-takers. While evidence shows that testing improves memory for tested material, this can include the incorrect material presented on recognition tests manifested as increased reproduction of incorrect answers (lures), a phenomenon known as the negative testing effect. These effects of testing, however, have only been studied in younger learners. Older learners, on the other hand, may show decreased positive testing effects and increased negative testing effects because of poorer long-term episodic and source memory, perhaps making them less receptive to the positive effects of testing and more susceptible to the negative effects of testing. Therefore, this study examined the positive and negative effects of testing on learning in 60 younger university students aged 18-25, 60 younger community adults aged 18-25, and 60 older community adults aged 55-65. This research also scrutinized how individual differences, including intelligence, previous knowledge, initial performance, and source memory were related to the positive and negative effects of testing. All groups showed positive testing effects, but these were larger for younger adults, for individuals with higher initial performance, and for people with more previous knowledge of the topics. Additionally, though no age group showed reliable negative testing effects, they increased for individuals with lower initial performance and previous knowledge and, surprisingly, for learners with higher nonverbal reasoning and verbal intelligence scores. These findings have important implications for the education of people of all ages and show that testing can be a beneficial learning tool for both younger and older learners.