Background: Antithrombotic therapy, such as acetylsalicylic acid (ASA) and clopidogrel, may interfere with platelet Aggregation in thrombotic strokes. Therefore, a platelet Aggregation test is essential for monitoring therapy. A previous study observed a decrease in platelet Aggregation using antithrombotics with a manual LTA analyzer. Further research is required to compare this with an automatic tool to determine whether both instruments have similar detection capabilities.Methods: PPP and PRP samples were collected from 30 thrombotic stroke outpatients and 30 healthy controls. Platelet Aggregation tests were performed using ADP 5µM and Collagen 2µg/mL on both instruments, Chronolog® Model 490, and Sysmex® CS-2500. The tests were then analyzed using the Wilcoxon test for differences, the Spearman test for correlation, and the Bland-Altman analysis for agreement.Results: No differences were observed in MA values and numerical alignment between the two instruments for ADP and Collagen. If the MA result for the platelet Aggregation test on Chrono-log® Model 490 was high, it was likewise high on Sysmex CS-2500 and vice versa. Although the values of LP and Vel differed, the numbers for ADP and Collagen in both instruments were consistent.Conclusion: The comparison between both instruments indicates good agreement. Automated LTA demonstrates the same suitability as manual LTA and can be applied in clinical routines to assess platelet Aggregation function. Due to many variations in the pre-analytics stage that might affect the results, it is vital to standardize both the pre-analytics, analytics, and post-analytics stages to compare platelet Aggregation tests on the two instruments.