Background: Nowadays, children spend a lot of time during the day in front of the television(TV) and using their phones. We aimed to evaluate screen time and phone use in Iranian children and their relation to the socioeconomic status of children's families.Methods: This descriptive analytical study was done on 10-12-year-old children from Kurdistan, Fars, and Markazi provinces. Cluster sampling was used for sampling. Date collection included completing demographic questionnaires, calculating BMI of children and phone & tablet use, screen time, and socioeconomic status. We used linear and logistics regression to estimate the final model and decomposition method of the Oaxaca. The concentration index and the concentration curve were used to measure and illustrate socioeconomic inequalities. All analysis was conducted with the Stata / SE 14.0 software.Results: 1590 children (52.58% boys) were enrolled in our study, 594 (74%) of boys and 420 (56%) of girls had daily Screen Time activities for more than two hours, and 388 (48.20%) of boys and 211 (28.20%) of girls use mobile phones and tablets for more than two hours a day. Screen Time activities were significantly higher in boys, older children, higher BMIs, more educated mothers, and 35<year-old fathers (P_VALUE <0.05). The use of mobile phones and tablets by boys, ten-year-olds, families of four or less, older BMIs, children with higher levels of parental education, and more educated mothers is significantly higher (P_VALUE <0.05). In addition, the Concentration Index for Screen Time activities (C = 0.083) and phone or tablet use (C = 0.536), shows that the Screen Time, phone or tablet use activities are higher in children with high socioeconomic status.Conclusion: The screen time activities and phone & tablet use are higher in children with high socioeconomic status. Also, many other factors like gender, age, BMI, parent's education, and age can affect screen time activities and phone & tablet use in children. It is recommended to measure the effectiveness of the changeable factors by modifying and controlling these factors in future studies.