This quantitative study was based on a parental intervention focused on children's language development. The Test de Vocabulario de Imagenes Peabody-III was used to assess children's vocabulary in Spanish pre- and post-intervention. The data was collected during five semesters from Fall 2015 to Fall 2017 from 421 economically-disadvantaged urban families, mostly Spanish-speaking immigrants living in Central Texas. Data used in this study came from a subsample of 204 families, whose children were aged 30 months and older. Paired-two-samples t-test demonstrated an increase in children's standardized vocabulary scores of about 3 times that expected by maturation alone. An ANOVA revealed that the children group having the lowest beginning vocabulary level had the greatest vocabulary growth. A positive and statistically significant relationship was found between the change in parental perceptions and attitudes of children's positive and problem behaviours and the children's vocabulary change.