This quasi-experimental study investigated the effects of an Internet-delivered universally designed depth of vocabulary intervention that targeted both English-speaking and Spanish–English-speaking students. Two hundred forty students, 49% of whom were Spanish–English bilinguals, participated in the 16-week intervention. Intervention students read eight multimedia texts with embedded instruction on 40 words and reading strategy support. Students could access all texts and activities in Spanish and English. In comparison to a control group, there were significant intervention effects on a standardized measure of vocabulary knowledge, but effects were non-significant for comprehension. Similarly, significant effects on researcher-developed measures of vocabulary depth were detected, but not for a researcher-developed measure of breadth.