Background: The immune system plays an essential role in maintaining physiological homeostasis, which can be reflected through total and differential leukocyte counts. Functional foods containing bioactive compounds, such as over-fermented tempeh (tempe semangit), have attracted attention due to their potential immunomodulatory properties. Objectives: This study aimed to analyze the differences in total and differential leukocyte counts before and after the consumption of tempe semangit cookies among students of SMK Karya Teknologi 2 Jatilawang. Materials and Methods: This study employed a pretest–posttest control group design involving 32 participants who were equally divided into control and intervention groups. The intervention group consumed tempe semangit cookies at a dose of 40 g/day for 7 consecutive days, while the control group received no treatment. Total leukocyte count and differential leukocyte parameters, including band neutrophils, segmented neutrophils, lymphocytes, and monocytes, were measured before and after the intervention. Data were analyzed using paired t-test and Wilcoxon test with a significance level of 0.05. Results: The results showed no significant change in total leukocyte count in the control group (p = 0.349), whereas a significant reduction was observed in the intervention group (p = 0.031). No significant differences were found in differential leukocyte counts within each group (p > 0.05). However, significant differences in lymphocyte (p = 0.029) and monocyte levels (p = 0.020) were identified between groups after the intervention. Conclusions: In conclusion, short-term consumption of tempe semangit cookies may exert immunomodulatory effects by influencing total leukocyte count and selected immune cell parameters without altering the overall leukocyte differential profile.