The aim of this study is to examine factors that affect secondary students' behavioural intention to use GeoGebra Augmented Reality to support a projectbased geometry learning environment. To achieve this purpose, we adopted technology acceptance model (TAM). A total of 54 students from two lower secondary schools in Indonesia were involved in this study. The students enrolled in secondary mathematics classes and attended six lessons of a project-based geometry learning assisted with GeoGebra Augmented Reality. Descriptive analysis, multiple regression and independent T-test were employed to analysed data. The findings of this study suggested that GeoGebra Augmented Reality was well accepted by the secondary school students. It was found that perceived of usefulness (PU) is the strongest factor of students' behavioural intention (BI). Contrary to the previous studies, this study showed that attitude toward using (AT) has no direct effect on behaviour intention (BI). We elaborate how the findings of this study could improve the understanding of AR acceptance by students and highlight important guideline for educational AR developers, researchers, and educators.