The aim of the current study was to investigate the mediating role of private speech in conceptual model of relationship of language development and secure attachment with self-regulation in children.128 children, aged 3-7 years old, from kindergartens in Tehran city were selected. Persian Version of Test of Language Development (Hassanzadeh & Minaei, 2002), Disturbances of Attachment Interview (Smyke & Zeanah, 1999), Self-Regulation Scale (Amrai, 2015), Preschool Children Behavioral Disorder (Shahim and Yousefi, 1999) and Structured Observation of Behavioral Regulation (Ponitz and et al, 2008) were administered on both mothers and their children. Path analysis was employed to analyze the data. The results showed that the model had reliable indices of fitness based on which language development and secure attachment had direct and indirect effects on behavioral self-regulation. In addition, private speech showed a mediating role in relationship of language development and secure attachment as well as self-regulation. The findings of present study facilitates prediction of children self-regulation based on language development and secure attachment with regard to the role of private speech as a mediator. Therefore, it is reasonable to suggest considering language development and attachment style of children as a way to reduce behavioral problem and improve self-regulation.