If geography teachers appreciate the important role of spatial thinking in their disciplines, they can proactively explore educational interventions to improve the spatial thinking of their students. Our understanding of geography teachers' perceptions around spatial thinking is still in its infancy. Until now almost all studies investigating spatial thinking in teachers have focused on pre-service teachers. Therefore, this study attempts to expand our understanding by exploring the perceptions of in-service geography teachers towards spatial thinking, spatial thinking instruction, and the factors that impact enactment of spatial thinking instruction. To achieve this goal, we conducted interviews with 15 geography teachers in Vietnam. The results show that teachers' understandings reflect three components of spatial thinking (concepts of space, tools of representation, and reasoning). However, their responses also reflect ambiguous and unclear understandings about spatial thinking. These findings can inform professional development for teachers in Vietnam.