Abstarct: Introduction and Aim: High-intensity interval training (HIIT), despite its mextabolic benefits, is associated with acute inflammatory responses and neuromuscular performance alterations, particularly in overweight individuals who are prone to movement limitations. The aim of the present study was to investigate the acute response of serum interleukin-6 (IL-6), explosive power, agility, and dynamic balance to a single session of HIIT in overweight men. Methods: The statistical population consisted of overweight men aged 30–40 years (body mass index: 25–29.9 kg/m²) from Shahroud, Iran. From this population, 20 participants were purposefully selected and randomly assigned to either a HIIT group (n = 10) or a control group (n = 10). The HIIT protocol included 5 minutes of warm-up, 8 one-minute bouts of activity at 85–90% of maximum heart rate, and 5 minutes of cool-down. The control group rested in a seated position for the same duration. Blood samples were collected before and immediately after the intervention to measure serum IL-6 levels via ELISA. Explosive power (Sargent jump test), agility (T-test), and dynamic balance (Y-balance test) were also assessed at both time points. Data were analyzed using repeated-measures analysis of variance (ANOVA) with a significance level set at P < 0.05. Results: The time × group interaction effect was significant for all variables (P < 0.001). IL-6 levels in the HIIT group increased from 6.33 ± 3.47 to 18.82 ± 5.96 pg/mL, while the control group showed a smaller increase (from 8.65 ± 6.14 to 13.77 ± 5.95 pg/mL; P < 0.001, η² = 0.563). Explosive power in the HIIT group decreased from 38.50 ± 2.80 to 33.40 ± 2.59 cm, whereas the control group exhibited no substantial change (P < 0.001, η² = 0.985). Agility time in the HIIT group increased from 13.23 ± 0.77 to 14.42 ± 0.72 seconds, indicating a performance decline, while the control group improved slightly (P < 0.001, η² = 0.988). Dynamic balance scores also decreased in the HIIT group, from 101.16 ± 5.57 to 94.54 ± 5.40, whereas the control group showed a mild increase (P < 0.001, η² = 0.990). Conclusion: A single session of HIIT, while provoking a significant inflammatory response (increased IL-6), simultaneously induces acute decrements in explosive power, agility, and dynamic balance in overweight men. This duality suggests that although HIIT is an effective mextabolic stimulus, the consequent neuromuscular fatigue may impair motor skill performance. Therefore, allowing sufficient recovery time prior to activities requiring high power, agility, and balance appears essential in this population.