This study investigated the impact of L-citrulline on glucose homeostasis, lipid profile, and inflammatory factors in overweight and obese patients with type 2 diabetes (T2D). In total, 54 participants with T2D were assigned to L-citrulline (3 g/day L-citrulline) or placebo groups and tested for 8 weeks. Serum levels of insulin, fasting glucose, hemoglobin A1c (HbA1c), lipid profile, tumor necrosis factor-α (TNF-α), high-sensitivity C-reactive protein (hs-CRP), and L-citrulline were measured pre- and post-intervention. Totally, 45 patients were enrolled in the research. L-citrulline supplementation decreased serum levels of insulin (p = .025), glucose (p = .032), HbA1c (p = .001), HOMA-IR (p = .037), TNF-α (p = .036), and hs-CRP (p = .027) significantly. At the end of the study, despite the significant decrease in serum levels of triglyceride (p = .027) and the increase in high-density lipoprotein cholesterol levels (p < .001) in the L-citrulline group, no significant differences were found for these parameters between the groups. Moreover, no significant inter- and intra-group changes were observed for dietary intakes, anthropometric indices, total and low-density lipoprotein cholesterol levels (p > .05). In conclusion, L-citrulline supplementation might improve glucose homeostasis, some lipid factors and inflammatory markers in overweight and obese patients with T2D.