Stuttering is considered as one of the most important speech disorders and general cognition among speech and language disorders (1). Persian-speakers with a stuttering problem demonstrate a different degree of prolongation, silence or block at the beginning and remedial review in different ages based on stuttering severity with stuttering changes from sentence and types; namely, the length, meaning and complexity of the word influences fluency deficit intensity.[H1] The purpose of this study was to investigate the relationship between stuttering severity and type of inflectional morphemes stuttered in 15–35-year-old stutterers with mild to moderate severity. 20 stutter participated in this study. 10 stutter with a mild stuttering problem and 10 stutter with a moderate one. Participants’ speech was recorded while they narrate a story (about 400 syllables) in a natural setting for 3–5 minutes. Then the speech was analyzed and the types of inflectional morphemes, which stuttered, were identified. Stuttering severity was also measured utilizing the SSI4 scale. Statistical analysis data was done by SPSS software and Spearman correlation test. Data analyses indicated that there is a direct and significant relationship between moderate stuttering severity and inflectional morphemes in particular types of verb prefixes ( P = .024), and there is a direct and linear relationship between mild stuttering severity and inflectional morphemes in type of verb prefixes ( P = .008), whereas this relationship was not statistically meaningful ( P < .05). Additionally, there is no significant statistical relationship between mild to moderate stuttering severity and inflectional morphemes) plural, indefinite, comparative and superlative, transient maker and identity verbs) ( P < .05). Results demonstrated the severity of stuttering was related to length, meaning and consonant complexity of morphemes. As stuttering severity reduced (mild and moderate), the effect of inflectional morpheme's type on stuttering, reduced.