Biochemical polymorphism study is a method of determination of genetic variation. This variability could be a basis for selection and subsequent genetic improvement in farm animals. The polymorphism in the intron 1 of chicken growth hormone (cGH) gene was investigated in the Iranian native fowls by using polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) method. The genomic DNA was extracted from 217 samples (129 samples from the native fowls of Isfahan province and 88 samples from the native fowls of Mazandaran province) by using modified salting out technique. The DNA fragment of the growth hormone gene with 776 bp was amplified by PCR using specific primers. Then the PCR products were digested with MspI restriction enzyme and analyzed on 2.5% agarose gel. The allelic frequency of intron 1 locus for A1, A2 and A3 alleles in  Isfahan native fowls were 0.60, 0.21 and 0.19 and those in Mazandaran native  fowls were 0.28, 0.05 and 0.67, respectively. The results of current study indicated that the intron 1 of cGH is polymorphic in Iranian native fowls and could be exploited as a candidate gene for marker-assisted selection for growth-related traits.