Background and Aim: Alzheimer’s disease is a common neurodegenerative disorder characterized by cognitive decline, memory impairment, and alterations in inflammatory and neurodegenerative pathways. This study aimed to investigate the effects of treadmill exercise and niacin supplementation on spatial memory and the expression of Alzheimer’s-related microRNAs in a streptozotocin (STZ)-induced rat model. Methods: In this experimental study, 30 male Wistar rats were randomly assigned to five groups (n = 6): control, Alzheimer’s, Alzheimer’s + niacin, Alzheimer’s + exercise, and Alzheimer’s + exercise + niacin. Alzheimer’s disease was induced via intracerebroventricular injection of STZ. Interventions were conducted for 30 days and included treadmill exercise and niacin administration (100 mg/kg). Spatial memory was assessed using the Morris Water Maze test, and microRNA expression levels were measured using Real-Time PCR. Data were analyzed using one-way ANOVA followed by Tukey’s post hoc test. Results: Alzheimer’s induction significantly impaired spatial memory (P < 0.05). All treatment groups showed a significant reduction in escape latency compared to the Alzheimer’s group (P > 0.05). Additionally, the exercise and combined groups showed a significant increase in time spent in the target quadrant, while all treatment groups demonstrated a significant increase in the number of platform crossings and a decrease in latency to first crossing compared to the Alzheimer’s group (P < 0.05). No significant differences were observed among treatment groups (P < 0.05). At the molecular level, all treatment groups showed a significant increase in miR-29a, miR-29c, and miR-9a expression and a significant decrease in miR-146a compared to the Alzheimer’s group (P < 0.05). The combined group showed greater increases in miR-9a and miR-29c, while the niacin group showed the highest increase in miR-29a.Conclusion: Treadmill exercise and niacin supplementation, especially in combination, improved spatial memory and modulated microRNAs associated with inflammation and neurodegeneration, suggesting protective effects in Alzheimer’s disease.