Teacher grit and teacher leadership are two qualities that are touted to improve teacher performance (Duckworth, Quinn & Seligman, 2009; Smylie, Lazarus & Brownlee-Conyers, 1996). However, few empirical studies have investigated the direct relationship between teacher grit and leadership and their direct effects on student achievement. In this case study, a survey of 22 teachers in a Malaysian international school was conducted using Duckworth & Quinn's (2009) short grit (Grit-S) questionnaire to measure grit, and Katzenmeyer & Moller's (2009) Teacher Leadership Self-Assessment (TLSA) questionnaire to measure leadership potential. The findings indicate that grit is positively correlated with five out of six of TLSA's leadership dimensions, except the diversity dimension. Using student results in a standardized examination, this study further found that differences in teacher grit or leadership potential do not result in significant differences in student achievement. The findings are followed by a discussion on the implications of the results on the emphasis of grit and teacher leadership in education reforms, and the limitations of this study.