Objective: The nocturnal blood pressure (NBP) reduction is less than normal in the patients with type 2 diabetes mellitus (type 2 DM). L-carnitine deficiency may cause changes of NBP by leading to hyperglycemia, insulin resistance and endothelial dysfunction in patients with type-2 DM. The purpose of the study was to investigate whether there is a difference in levels of L-carnitine in dipper and nondippers patients with type 2 DM. Methods: This is a cross-sectional observational cohort study. We compared the 50 (33 females, 17 males) patients with type 2 DM and the 35 healthy persons (18 females, 17 males) as a control group. In all cases, ambulatory blood pressure monitoring (ABPM) was performed and L-carnitine was measured. The independent samples t test, Chi-square test, Mann-Whitney U test and Pearson correlation analysis were used in the statistical evaluation of data. Results: We found that the percentage of nondipper pattern was 72% in patients with type 2 DM. L-carnitine levels were lower in patients with type 2 DM (52.77±12.34 μmol/L) than those of control group (79.18±10.59 μmol/L), and these differences were statistically significant (p<0.05). L-carnitine levels were lower in nondipper cases (50.02±16.30 μmol/L) than those of dipper cases (53.83±10.50 μmol/L), but these differences were not statistically significant (p=0.125). Conclusion: Nondipper pattern is common in patients with type 2 DM. Nondipper pattern is associated with damage of target organ. Therefore, determination of nondipper pattern by ABPM is very important. L-carnitine levels were found to be lower in nondipper patients than in dipper patients with type 2 DM. Although, these differences were statistically nonsignificant, more detailed studies should be performed to determine the frequencies and relationship between nondipper pattern and L-carnitine levels in patients with type-2 DM.