Factor XIII deficiency (FXIIID) is an extremely rare autosomal recessive disorder that has the highest incidence in Iran. The FXIIID is primarily due to mutations in the FXIII-A gene, most of which are unique. In the current study, we report all identified mutations among Iranian patients. Among 483 patients, 366 (75.8%) were molecularly analyzed; 11 different mutations were observed. Of 11, 8 (72.7%) are missense, whereas the remaining 3 (27.3%) are deletion/insertion. Among these patients, 347 (94.9%) had the unique mutation of c.562T>C and 5 (1.4%) had the c.233G>A mutation. c.1226G>A, c.2111G>A, and c.1142T>A are also common, whereas other mutations, including 3 missense and 3 deletion/insertion, were observed only in single patient. Although, in most cases, FXIII mutations are unique and restricted to a specific family, this differs in Iran where a considerable number of identified mutations, recurrently observed, appear to be due to the high rate of consanguinity.