Teachers' varied goal orientations meaningfully explain differences in their behaviour and cognition. Achievement goal orientation theory (GOT) provides a valuable theoretical framework for understanding teacher motivation. However, GOT has not yet been applied in the context of mentoring student teachers during the practicum. This study explores the use of GOT and describes mentor teachers' motivations during the school practicum. For this, we analyse semi-structured interviews with 23 Austrian mentor teachers using qualitative structuring-content analysis. Results show that within the mentoring context it is important to differentiate between self- and other-oriented goal orientations. Mentor teachers are strongly mastery and relational goal oriented, while ability-avoidance and work-avoidance goals are less prominent. Overall, the findings demonstrate GOT's value in understanding mentor teachers' motivations. Implications are offered as an avenue for future research.