Mistakes are at the crux of daily classroom learning. This is the case even in the earliest grades. While the instructional value of mistakes is wellknown among educators, little research documents how young children experience mistakes in real-world school settings. In the present study, I conducted semi-structured interviews with 25 Kindergarten teachers about responses to mistakes in their classrooms. I identified commonly-reported types of mistakes teachers indicated that young children make in the classroom and the students' corresponding affective responses. Some frequent categories of mistakes teachers reported were (a) content-specific misunderstandings like inaccurate counting and letter reversals, (b) process mistakes stemming from not listening to directions and rushing through work, and (c) behavioral/social infractions that included breaking class rules or being unkind to other children. Results indicated various affective responses children have toward mistakes, which were either disagreeable, like shutting down or crying, or agreeable, like maintaining a calm demeanor or laughter.