Introduction:Children say the first words in the end of their first year of life. As children grow, the number of words and phonemes in their phonetic inventory increases.The first appearing consonants in the children's phonetic inventory are nasal, plosive, fricative, labial and lingual phonemes. The older a child, the more his/her usage of various types of consonants.In order to make a decision about the appropriateness of children's speech, speech and language pathologists need the evidence that comes from the studies focusing on different aspects of speech development. The aim of the present study was to determine the acquisition age of consonants in Farsi- speaking children.Materials and Methods:The present research was a cross-sectional descriptive - analytic study. Speech samples of 96 2-6 year-old Farsi-speaking children who lived in Tehran (Iran) were recorded and then analyzed. Through 44 pictures, 22 consonants of Farsi were studied in final and first positions of mono and two syllabic words.Results:Nasal and plosive bilabial consonants /b/, /p/, and /m/ were the first consonants pronounced correctly in both positions of words by 2-2/5 year-old children. The fricative and affricative consonants /ž/ and /ĵ/ were the last ones emerged correctly in both positions, that is to say, after the 4th year of life. According to the Regression test results, this hypothesis that the number of children's consonantal errors decreases as they grow, was confirmed.Conclusion: By the 4th year of their life, Farsi-speaking children can correctly produce all consonants in both final and first positions of mono and two syllabic words except /ž /, /ĵ/. These findings are consistent with the similar studies done in English language. Fricatives are also the most difficult consonants in English language.