We use three studies to develop and validate the new concept of playful study design -- the cognitive-behavioral orientation towards study tasks with the aim to make these tasks more fun and/or more challenging. Based on play and proactive motivation theories, we propose that playful study design can be assessed by items indicating two dimensions: designing fun and designing competition. Results of exploratory (N = 378 students) and confirmatory (N = 375 students) factor analyses support the two-factor structure of the playful study design instrument in a first study. In addition, we use the data of the whole sample of Study 1 to test the convergent and incremental validity of the construct. Results indicate that playful study design predicts students' social integration, study engagement, and well-being over and above psychological capital and core self-evaluations. In Study 2 (N = 591 students), we used playful study design to predict course grades. Results show that particularly designing competition was beneficial for study performance. In Study 3 (N = 28 students), we conducted a quasi-experimental evaluation of a training intervention to demonstrate that students who learned to playfully redesign their study tasks increased their use of fun and competition when studying. As a result, they showed greater active learning, study task proactivity, and absorption over time compared to the control group. We discuss how the construct of playful study design adds to the educational psychology literature and has implications for educational practice in university settings.