The current explorative study aimed at understanding the subjective meanings of "compassion" in teaching and its process and determinants. Based on 14 semi-structured interviews with teachers who are considered by their colleague to be compassionate, it was found that compassion consists of two phases--identification and compassionate behavior, and triggered by varied sources of suffering (e.g., distress at the student's home, academic failure, chronic illness, exam anxiety, school violence, and special education needs). Likewise, four major factors of compassionate behavior in teaching have been identified: personal background, career experience, close teacher--students relations, and educational leadership. Theoretical and practical implications are discussed.