This study examined the efficacy of using different types of mobile media apps to increase the receptive and expressive vocabulary development of 3-, 4-, and 5-year-old preschool children living in economically disadvantaged communities. Children and teachers in four Head Start classrooms participated in the quasi-experimental study, which included an 8-week intervention in which the children interacted with one of two types of apps: one classroom used four scaffolding-like vocabulary apps for an average of 1.8 h per day (n = 16) and one classroom used four open-ended vocabulary apps for an average of 1.3 h per day (n = 15). Two classrooms served as comparison groups (n = 18; n = 14) which used apps that were chosen by the Head Start program with no specific instructional method for approximately 1 h per day. Children's vocabulary was assessed pre- and post-intervention using the PPVT-4, the EVT-2, and iPad Receptive and Expressive Vocabulary Assessments. Using a repeated measures analysis of variance with split plot analysis, children who used scaffolding-like vocabulary apps performed statistically significantly higher on the PPVT-4 than children who used open-ended vocabulary apps. There were no significant differences between groups on the EVT-2. The study contributed to the literature on teacher instruction of utilizing scaffolding-like apps to increase preschool vocabulary knowledge. (author abstract)