Objective: 1) To differentiate various connective tissue layers in radicular cysts 2) To find the correlation between FXIIIa containing cells and fibrosis. Factor XIII, fibrin stabilizing factor, stabilizes the clot for blood coagulation and is also responsible for connective tissue organization in healing and tissue repair. FXIIIa has an important role during the process of fibrosis in various lesions, so we conducted a study to find its role in radicular cyst. Study Design: 10 cases of radicular cyst, reported in our hospital were selected. Clinical and follow up data of those cases were collected from the archives. Material and Methods: Histochemical analysis with Masson’s trichrome was done to differentiate the three layers of radicular cyst. Immunocytochemical staining for distribution of factor XIIIa was carried out. Stained slides were examined under high power. After counting cell, data was analysed statistically. Results: Positive reaction for Factor XIIIa was observed in certain connective tissue cells in all the layers of radicular cysts. FXIIIa containing cells were numerous in intermediate layer as compared to outer fibrous layer. FXIIIa containing cells and fibrosis was increased in case of radiographically well circumscribed lesion than the diffuse lesion. It can be concluded that factor XIIIa containing cells and collagenous components in radicular cyst play an important role in fibrosis and is also correlated with healing of the lesion.