This study aimed to investigate the following questions: Does the use of thinking maps and semantic mapping during explicit vocabulary instruction affect content specific science vocabulary knowledge and comprehension in fourth grade students? and What are student perceptions of using thinking maps and semantic maps to learn new vocabulary? To address these questions, 44 fourth grade students from an elementary school in a northeastern city in the United States of America participated in a mixed-method quasi-experimental study over a six week period. Using a pre-experimental design, two intact groups received explicit instruction on how to use thinking maps and semantic maps to develop vocabulary definitions for a selection of tier two and tier three vocabulary words from the Pearson Interactive fourth grade science curriculum (Buckley et al., 2016) and PSSA released assessment items (Pennsylvania Department of Education, 2021). Pretests and posttests measured vocabulary knowledge (Vocabulary Size Test, Nation & Beglar, 2007) and science comprehension (PSSA, Pennsylvania Department of Education, 2021). Semi structured verbal interviews were conducted at the conclusion of the six week intervention period and were analyzed using emerging codes. Results of the VST and PSSA released items assessment were compared using two separate, one-way ANOVA with repeated measures to identify any variation and difference of means between pretest and posttest scores of the participants (43 students) after intervention. Quantitative results revealed that there were no significant statistical differences in vocabulary knowledge measured by the VST or the PSSA released items assessment. However, qualitative data collected from student interviews supports that students had positive experiences using thinking maps and semantic maps and felt that these tools helped them learn new science vocabulary. [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.]