This study aimed to investigate the differences between different groups of students in mathematical problem-solving and metacognitive skills. The study sample included ninety students in grade 6. These students were distributed into three groups as following: 30 students were included in a learning disability program, 30 students were considered average-achieving students and 30 were considered high-achieving students. There were two main purposes for this study. First, it aimed to investigate the differences between the three groups in mathematical problem-solving and metacognitive skills according to group type and gender. Second, it examined the relationship between mathematical problem-solving, metacognitive skills, intelligence test scores (Raven Colored Progressive Matrices) ,long-term memory scores and age. The findings indicated that there is a significant difference between the three groups in both mathematical problem-solving and metacognitive skills, while there were no gender differences in mathematical problem-solving or in metacognitive skills. Students in the learning disability program showed the lowest performance when compared with the other two groups. This study also found that there was a significant relationship between mathematical problem solving, metacognitive skills, intelligence test scores (Raven Colored Progressive " Matrices,), long term memory scores. Also, there was no significant difference between the two scales of metacognition skills (verbal and non-verbal) which means that they alternatively measure similar dimensions. This study suggests that metacognitive skills can potentially contribute to successful mathematical problem solving.