This study aimed to reveal the common errors in fractions, the associated thinking strategies among 5th graders, and the persistence of these errors. A quantitative method was applied in this study through calculating the percentages of every type of error the students made in the diagnostic test, The qualitative part was performed through individual interviews and analyzing them to probe the thinking strategies used by the students that lie behind their common errors, The test was conducted for 240 students and 30 students were interviewed. The results showed a variety of common mistakes the students made, and that the rates of these mistakes were as follows: the highest was due to dealing with the fractions as integers, followed by errors about the basic concepts of the fractions. The results further showed a diversification in the students' thinking and the associated mistakes. One of the most noticeable mistakes was expressing the fraction without attention to the equal parts. The rates of other common errors were as follows: considering that the fractional number is always higher than the figure A/B, and that figure A/B is always less than one; treating the fractions as integers; misinterpretation of the relation between the numerator and the denominator with the actual value of the fraction, and ignoring the integer in the fractional number. The results also showed that more than 50% of the students made errors associated with solution strategies in the fractions issue.