Children's early language development is under the influence of several positive and negative factors including television as an input source and family's socio-economic status. Considering that, this study investigated the effects of these variables on children's vocabulary development using a quasi-experimental design. To this end, 60 Iranian children, 30 from high and 30 from low socio-economic status, were selected using stratified random sampling. They were divided into four groups based on their background TV exposure and socio-economic status. TOLD-3 was given to the groups as a vocabulary development test before and after a 6-week observation. Results indicated that the high socio-economic-low background group scored higher than the other groups in the vocabulary development posttest while the low socio-economic-low background group scored lower that the other groups. Furthermore, while high background TV had a negative influence on the children's vocabulary development in families with a high socio-economic status, it had a positive influence on the children in families with a low socio-economic status. These results have some implications for families, first and second language studies.