The purpose of this study was to examine the effects of extended vocabulary instruction on the expressive vocabulary of two third-grade students with vocabulary deficits. According to the Common Core State Standards Initiative (n.d.), students in third grade should be able to determine the meaning of unknown and multiple-meaning words and phrases based on grade-level material, demonstrate an understanding of word relationships, make real-life connections with words and how they are used, and recognize shades of meaning among similar words. There is a relationship between vocabulary and comprehension (Ouellette, 2006). Furthermore, making inferences is also important for comprehension (Hall & Barnes, 2017). This study demonstrated the effectiveness of extended vocabulary instruction for supporting participants' target word knowledge and inferencing skills through a single-case multiple probe across word sets design. Two participants enrolled in third grade demonstrated increases in target word knowledge and inferencing skills. Implications for practice are discussed. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]