Background: Mast cells can influence tumor progression via different pathways and increased mast cell density has been demonstrated in oral squamous cell carcinoma (OSCC). It has been shown that the serum tryptase level is elevated with some malignant tumours and may thus be a useful parameter. However, there are no data available about OSCC. The main aim of this study was the evaluation of mast cell tryptase (MCT) level in OSCC patient serum. Materials and Methods: In this cross-sectional, analytic study, the circulating levels of MCT were assessed in sera of 55 OSCC patients and 34 healthy individuals with ELISA technique. Results: The serum MCT level in OSCC patients was 12-14 ng/ml, which was not significantly higher than the healthy control group. While the serum level of MCT was higher with larger tumours, there was no apparent correlation with clinico-pathological features such as patient age, gender, tumor location, stage, nodal status, distant metastasis, histological grade and smoking. Conclusions: Our findings showed that despite the results obtained from studies of other malignant tumors, serum level of MCT in OSCC patients could not be a credited as a reliable indicator of the presence or progression of tumours.