To support professional competence development in teacher education, learning environments should allow learners to engage with professional tasks. It is crucial for knowledge and skill transfer in such learning environments to real-life context that preservice teachers perceive the task as authentic. However, due to a lack of prior knowledge, novices may have difficulties in recognizing relevant elements of practice. It is thus assumed that different factors may guide their perception of task authenticity independently of the task that has to be mastered. Such factors could be, for example, overt design features of the learning environments on a physical level or the familiarity with the learning context and learning prerequisites, which act as important links for knowledge acquisition. In this study, preservice teachers' perception of task authenticity is contrasted between two implementation types (video vs. role-play) of the same simulation aiming to foster diagnostic competence. The two types differ in approximating real-life practice concerning the professional task that has to be mastered. In an experimental, longitudinal study, N = 119 mathematics preservice teachers participated online in one type of the simulation four times during one semester (n = 66 video, n = 53 role-play). Perceived task authenticity was higher for the video simulation type and increased with repeated participation in the simulation independently of the implementation type. Further, preservice teachers' task utility value positively influenced their perception of task authenticity. The results illustrate the role of learning prerequisites as well as familiarity with the task for novices' perception. Also, they could be an initial indication that, depending on the level of learners' professional development, the way of approximating real-life practice in simulations might influence the perception of task authenticity.