Introduction: Diabetes is a metabolic disorder with debilitating complications which affects several million people worldwide. Cardiac Autonomic Neuropathy (CAN) is the most common chronic complication of type 2 diabetes mellitus (T2DM), which is concealed for long period of disease. Heart rate variability (HRV) test is the simple and sensitive test for CAN. Diagnosing CAN at subclinical stage and knowing the correlation of HRV with duration of diabetes can help to prevent the morbidity and mortality because of this neuropathy. Objective: This study aims to determine the correlation of HRV with duration of diabetes in type 2 diabetes mellitus. Materials and Methods: This cross sectional study was conducted in Department of Physiology, in collaboration with Rajeev Gandhi Centre for Diabetes and Endocrinology on patients of T2DM attending Diabetes clinic in Jawaharlal Nehru Medical college hospital (JNMCH), AMU, Aligarh, from 2014 to 2016 after approval from the ethical committee of J. N. Medical College. Total 90 subjects were taken, among whom 60 subjects were diagnosed cases of T2DM, which were divided in two groups on the basis of duration of diabetes. Rest 30 subjects were non diabetic control group. For CAN heart rate variability test was done. Statistical analysis was performed using SPSS version 21.0. Results: In shorter duration Diabetes (3.31 __ampersandsignplusmn; 1.72 years T2DM), significant (p value__ampersandsignlt;0.05) negative correlation was seen between duration of diabetes and pNN50, RMSSD, HF power and LF/HF ratio, while in longer duration of Diabetes (12 __ampersandsignplusmn; 4.42 years T2DM), there was significant (p value__ampersandsignlt;0.05) negative correlation between duration of diabetes and all four HRV parameters, namely, pNN50, RMSSD, HF power, LF power, LF/HF ratio. Conclusion: Chronic hyperglycemia in diabetes leads to the degeneration and damage of autonomic nerves.