The aim of the study is to reveal the characteristics of proofs produced in calculus area by preservice primary mathematics teachers. In order to achieve this aim, proofs produced for the theorems on the basic issues of the calculus of preservice teachers were examined. This study, adopted qualitative research approach, is a case study. The research group of the study consisted of eight junior preservice teachers studying in the program of primary mathematics education at a state university in Turkey. The data of the study was collected with the help of task-based clinical interviews. Each preservice teachers were interviewed four times. The interview forms include true mathematical prepositions and formal definitions which are required for preservice teachers in proving process in functions, sequences, limit-continuity, and derivative concepts, respectively. Preservice teachers were asked to make a decision about whether the propositions were true or not and to verify decisions they made. It was seen that preservice teachers had difficulty in the producing correct proof although they hadn’t had any difficulty in choosing true prepositions. It was emerged that the proofs produced by preservice mathematics teachers had nine distinctive features: correct proof, partially correct proof, invalid proof, explanations, validation with the example, manipulation of definitions, copying definitions, incomplete proof and hypothesis writing. Moreover, while the preservice teachers with high academic success level had mostly the deductive proof scheme, preservice teachers with the average success level were in deductive, inductive and external proof schemes.