The aim of the study presented here was to identify the existence of a relationship between cognitive competence, the use of metacognitive strategies and the understanding of error in solving mathematical problems with 1st degree algebraic equations in 8th grade students. The results indicated important relationships between cognitive competence, the use of metacognitive strategies, error comprehension and problem-solving performance. These results highlight the need to develop activities in the classroom aimed at training students in the correct use of metacognitive strategies, with a view to improving their ability to solve mathematical problems, as well as preventing and understanding the errors they make.