Children\u27s letter knowledge is a strong predictor of later reading ability. However, there is limited research information on the relation of early childhood teacher instruction and classroom literacy environment to children\u27s letter knowledge. The current study examined: 1) associations among teachers\u27 explicit instruction in letter knowledge across three activity contexts (book reading, other large group activities, and free play period) and the literacy environment, 2) the relation between overall letter knowledge exposure (teacher instruction and literacy environment) and children\u27s letter knowledge growth across one semester, and 3) possible unique contributions of teachers\u27 explicit instruction in letter knowledge and the classroom literacy environment to growth in children\u27s letter knowledge. The sample included 31 Head Start teachers/classrooms and their 262 children. The results revealed that teachers\u27 explicit instruction during book reading and other large group activities were significantly related. The association between overall letter knowledge exposure and children\u27s letter knowledge growth demonstrated that the literacy environment and teachers\u27 explicit instruction did not work together to promote children\u27s letter knowledge. Neither teachers\u27 explicit instruction in letter knowledge nor the classroom literacy environment was uniquely associated with growth of children\u27s letter knowledge. Results suggest that teachers\u27 explicit instruction and the classroom literacy environment compensate each other in supporting children\u27s letter knowledge