This study examines the role that technological pedagogical content knowledge (TPACK) plays in elementary teachers' adoption of 1:1 computing for instruction across the subject areas of mathematics, science, English language arts, and social studies. In particular, the research explored whether teachers' self-reported TPACK moderated the relationship between teachers' perceived ease of use (PEOU) and perceived usefulness (PU) of 1:1 computing for instruction in each of the subject areas. The results indicated that TPACK was a significant moderator of the relationships between PEOU of 1:1 and whole-class science instruction, individualized science instruction, and individualized mathematics instruction. TPACK was also a significant moderator of the relationship between PU of 1:1 and the use of 1:1 for whole-class science instruction and individualized mathematics. TPACK was not a significant moderator of any of the relationships between PEOU or PU and instruction involving 1:1 in the subjects of English language arts or social studies. These findings suggest that TPACK can strengthen elementary teachers' adoption of 1:1 for instruction in mathematics and science but did not support this notion in English language arts or social studies.