This pilot study investigated the effects of a 20-week quasiexperimental vocabulary intervention aimed at improving Spanish-speaking language minority students' English vocabulary and writing outcomes. Participants were two matched samples of fifth graders (N = 49) in a predominantly Latino, low-income urban school. Pre- and posttest analyses revealed that the treatment group gained knowledge of a larger number of target words than did the contrast group and that the treatment group students were generally better at determining their own word knowledge. Further, individual growth modeling revealed the treatment students' overall writing quality improved over the course of the 20-week intervention, even though writing instruction was not part of the intervention, and improvements in students' writing quality were larger during the last 10 weeks of the intervention. The need for purposeful activities that provide students with authentic contexts to learn and productively use newly taught words is discussed. (Contains 4 tables, 1 figure and 4 footnotes.)