Adolescent students require strategies that are tailored to the specific linguistic demands of curricular vocabulary to support their decoding, spelling, and comprehension of novel big words encountered in texts. In this article, the authors describe a morphological instruction approach for helping students navigate big words in science. Reasons why big words in science are particularly challenging for many students are described, and guidelines for selecting and prioritizing high-utility science morphemes for targeted instruction with adolescent readers are provided. Specific strategies and examples are given, including a detailed example of a lesson that teaches students how and why to use morphological strategies to assist in their decoding and comprehension of unknown big words in science texts. Lists of high-utility science affixes are also provided.