Spanish-English cognates (words from ancestrally related languages similar in appearance and meaning) are plentiful in students' reading materials, but few researchers have documented elementary-age bilingual (Spanish-English) students' actual use of cognates. The authors drew from two qualitative research studies to show how bilingual students can be taught to use cognates to improve their spelling, writing, and reading. The third-grade teacher's instruction included a cognate definition and examples, identification of the written similarities and differences in Spanish-English cognates, and the completion of cognate lessons related to the students' English instruction on electricity. The fourth graders received cognate instruction to support their English reading comprehension. After instruction, most of the third graders used cognates for spelling and writing but not for reading, whereas most of the fourth graders used cognates to improve their English reading comprehension. Recommendations are made for how to teach cognates to bilingual students in bilingual, English-only, and English as a second language classrooms.