Introduction: The purpose of this study was to evaluate the expression of Interleukin-1 beta (IL1b), Tumor necrosis factor alpha (TNF-a) and Myeloperoxidase (MPO) in diabetic rats after pulp capping with Mineral Trioxide Aggregate (MTA) and a new endodontic Calcium Enriched Mixture (CEM) cement.Materials & Methods: To examine the effect of MTA or CEM, on diabetic dental pulp, animal model of Streptozotocin (STZ) -induced diabetic rats (intraperitoneal (IP) injection of STZ (65mg/kg) were used. Thirty four rats were divided into two diabetic and healthy groups. After exposing the pulp of the first maxillary molar, either MTA or CEM were used as pulp cap agent, cavities were sealed with resin modified glass ionomer cement. After thirty days, the rats were sacrificed. Chi-square, Pearson and two-way ANOVA tests were used for statistical analysis (a=0.05).Results: There was no significant difference in the amount of IL-1b, TNF-α and MPO between healthy and diabetic rats in MTA group (P=0.827, P=0.948, P=0.365). In CEM group, no difference in the amount of IL-1b and TNF-a between healthy and diabetic rats was detected (P=0.652, P=0.932). But there was a significant difference in the amount of MPO between healthy and diabetic rats in the CEM group (P=0.033).Conclusion: There was no significant difference between diabetic and healthy rats in the amount of IL1b, TNF-a in both MTA and CEM groups while the amount of MPO showed a significant difference in rats treated with CEM.