Objective: Children with ADHD show attention-switching impairment. The present study assessed attention-switching ability in adults with ADHD, the extent to which this ability can be improved via targeted training, and the degree to which training extends to novel tasks of attention-switching. Method: Adults with ADHD (n = 16) and adults without ADHD (n = 18) were divided into training and non-training groups. Training groups performed six blocks of four different attention-switching tasks, while non-training groups completed non-switching, “filler” tasks. Lastly, the four groups were tested on two novel attention-switching tasks. Results: Adults with ADHD showed impaired attention-switching, relative to non-ADHD adults, but training significantly improved attention-switching in both ADHD and non-ADHD training groups. Finally, training effects transferred to new tasks of attention-switching. Conclusion: Adults with ADHD show attention-switching impairments, but deficits may be ameliorated with short-term, targeted training. Research has implications for cognitive training in ADHD.