The purpose of this study was to explore pre-service and in-service mathematics teachers' analyses of student learning in a video case of mathematics instruction via an online learning forum. The study was conducted in the context of three different mathematics methods courses in a 4-year college in the Midwestern United States. Twenty-six students (19 undergraduate and 7 master's students) participated in the study. As a course assignment, the participants were asked to watch and discuss a video case of mathematics instruction. During the discussions, the instructor and participants posted 57 online messages in total. To analyze the data, the content analysis technique was employed. As the initial coding framework, National Council of Teacher of Mathematics [NCTM] Process Standards including problem solving, reasoning and proof, communication, connections, and representation were selected. The analysis of the data revealed that effective student participation, the importance of communication among the students as well as between the students and their teacher, the necessity of using connections among mathematical ideas, use of manipulative, using what students have already learned in a new situation, and building knowledge through problem solving were identified as evidence of mathematics learning by the participants.