This study examines the factors that affect pre-service and in-service teachers' intention to use Mobile Augmented Reality (MAR) in their teaching through the proposed Mobile Augmented Reality Acceptance Model (MARAM). The MARAM builds on the existing Technology Acceptance Model (TAM) to incorporate four other components namely perceived relative advantage, perceived enjoyment, facilitating conditions, and mobile self-efficacy. In addition, this study investigates the validity of the MARAM. Data were collected from 137 pre-service and 169 in-service teachers who completed a questionnaire after having developed their own MAR applications during an undergraduate university course and a training seminar, respectively. Structural Equation Model (SEM) analysis was conducted separately for each group, as well as for both samples together. We also conducted a multi-group analysis to examine differences across the two samples. The results for both samples together (N = 306), showed that intention was affected by attitude, perceived usefulness and facilitating conditions. In turn, attitude was affected by perceived enjoyment and perceived usefulness. Perceived usefulness was affected by perceived enjoyment and perceived relative advantage. Perceived ease of use was affected by mobile self-efficacy and facilitating conditions. However, perceived ease of use did not affect perceived usefulness or attitude. A multi-group analysis conducted on the sample of pre-service and in-service teachers produced similar results, with minor differentiations. These results have implications for the use of MAR in research and schools, as well as technology acceptance models in education.