Multitasking performance is relevant in everyday life and job analyses highlight the influence of multitasking over several diverse occupations. Intelligence is the best single predictor of overall job performance and it is also related to individual differences in multitasking. However, it has been shown that working memory capacity (WMC) is related to both intelligence and multitasking performance. Here we consider the simultaneous relationship among intelligence, WMC, and multitasking. The sample comprised three hundred and two applicants for air traffic control training courses. The main finding shows that intelligence and WMC are both related to multitasking, but only WMC predicts multitasking when their simultaneous relationship is considered. Furthermore, the processing and storage components of WMC predict multitasking performance. From an applied perspective it is suggested that WMC might be a relevant measure for personnel selection settings involving multitasking requirements. (Contains 1 table and 8 figures.)