The importance of calculus in mathematics, mathematics education, and other the necessity developing understanding regarding integral, which is one of the major concepts in calculus course, are among the issues emphasized by researchers. Thus, the purposes of this study were to examine how pre-service middle school mathematics teachers describe definite integral and indefinite integral and also to what extent they can see the relation between definite integral and indefinite integral. For these purposes, 173 pre-service middle school mathematics teachers were asked to answer three questions. According to the findings, the concepts pre-service middle school mathematics teachers mentioned while describing both definite and indefinite integral are similar which are bound, notation, mathematical formula, example, area, volume, antiderivative, calculation process, the form of result (number, function, algebraic expression or unknown), and the constant c. It was also seen that mostly mentioned concept is bound for each type of integral. However, the minority of them presented evidence regarding the relation between definite integral and indefinite integral in their responses.