Background: Acute exercise has been shown to positively impact working memory, but the influence of cognitive demand exercise on these effects remains unclear. The study aimed to investigate the effects of acute exercise with high (HE) and low (LE) cognitive demand exercise on working memory performance and neurophysiological indices in young adults. Methods: The present study applied a three-arm crossover randomized design, 31 participants completed three 20-minute conditions: HE, LE and active control (AC). Before and after the exercise intervention, working memory was assessed using 2-back task (reaction time and accuracy), the neurophysiological indices was measured using P300 (amplitude and latency). Results: The present study found a significant reduction in 2-back reaction time following both HE ( p =.005, d = -0.542) and LE ( p =.005, d = -0.423) compared to AC, with no differences between HE and LE. Futhermore, the shortening of P300 latency was significantly greater in HE than in LE ( p = .039, d = -0.419) and AC ( p < .001, d = -0.731), while P300 amplitude did not differ among conditions. Conclusions: The present study suggests that 20 minutes of moderate-to-vigorous interval training enhanced working memory in young adults, regardless of cognitive demand. A shorter P300 latency in the high-demand condition, however, indicates that cognitive demands during exercise may influence neural efficiency.