The vocabulary deficit shown by English Learners (ELs) has become evident among many educators over decades of research (Becker, 1977; Biemiller, 2001; Chall, Jacobs, & Baldwin, 1990; Hart & Riseley, 2003), and has shown that a student's limited vocabulary becomes a "major barrier to school success" (Graves, 2005, p. 18). Therefore, five fifth-grade ELs from John M. Clayton Elementary School participated in this nine-week study to determine the effectiveness of using context clues to define unknown vocabulary words and using semantic mapping to increase in-depth vocabulary knowledge. Participants received direct instruction using Graves's (2005) four-step process to define unknown vocabulary words using context clues until they were independently utilizing the strategy on their own. Along with this process, participants used semantic mapping to track their understanding and connection between vocabulary words in a unit of study before, during, and after reading a curriculum text to deepen their overall knowledge of vocabulary words. After implementing these two change ideas for nine weeks, all five participants in this study showed improvement across two process measures collected in this study, weekly quizzes and written comprehension responses. The five participants also showed an average of 64.75% improvement on an outcome measure testing overall reading comprehension on a unit test. Therefore, this study demonstrated that effective in-depth vocabulary instructional strategies positively impact reading comprehension for the fifth graders included in this study. Future research and professional development focused on vocabulary instructional strategies could provide continued improvement for the reading comprehension of ELs. [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://www.proquest.com/en-US/products/dissertations/individuals.shtml.]