The aim of this study was to reveal the effects of video-taped micro teaching, if used as a tool for formative assessment, on preservice language teachers' both teaching and foreign language anxiety. By the use of Student Teacher Anxiety Scale (STAS) and Foreign Language Classroom Anxiety scale (FLCAS), the data were collected from the non-native preservice language teachers in a state university. The results showed that these preservice teachers felt a high teaching and foreign language anxiety before and during their micro teaching sessions. However, after formative use of video-taped micro teaching, preservice language teachers' teaching and foreign language anxiety lowered to a moderate level. The study suggests that micro teaching, one of the most effective ways in teacher training, can be a more effective way if it is assessed formatively.