This study aimed to investigate the effectiveness of using a mobile Augmented Reality (AR) application in the geography unit for 10th grade students on their achievements and attitude. The unit is part of the Omani's social studies curriculum and entitled, "Environmental Problems and Hazards". To achieve this purpose, a quasi-experimental study design was conducted. The instruments were designed, validated and used to collect data from the pre-post achievement test and attitudinal scale. The participants were 64 male students, divided into the experimental and control groups. The field application treatment took four weeks in which the control group studied the unit using the normal teaching method, while the mobile AR application, HP Reveal, was integrated to teach experimental group. The findings showed that there was a statistically significant difference between the pre- and post-field application in terms of students' achievement and attitudes. Nevertheless, there was no impact observed when the control and experimental groups' achievement were compared. The researcher suggested to conduct further investigations to examine the value of integrating AR in the educational system considering various factors and variables.