The aim of this study was to investigate the effect of airborne PM2.5 particles on neonatal growth indices at birth. The present research is a causal-comparative and correlational study. Data were collected in two stages. To obtain monthly and annual reports of air pollutants in different areas of Tehran, the site of Tehran Municipality was referred to, and areas 1 and 2 as the cleanest areas with PM2.5 and areas 11 and 19 with the highest levels of pollution were chosen. In the second stage, the health centers of these areas were referred. The details of 400 infants and mothers were randomly collected based on the national code. Data were analyzed using Pearson correlation test, one-way analysis of variance and LSD test. The results showed that there was a significant positive correlation between maternal age and number of deliveries with height, weight and head circumference of the baby as well as maternal weight with height and head circumference of the baby (P <0.05). But there was no significant relationship between maternal and infant weight (P> 0.05). Also, the results showed that living in different areas has a significant effect on the components of height, weight and head circumference of the child (P <0.05). According to the results of the present study, it can be said that the concentration of PM2.5 particles in the air as a teratogen may affect the growth indices of newborns in Tehran and there is a relationship between some characteristics of mother and infant at birth.