Background: Online and blended learning need an appropriate assessment strategy which ensures academic integrity. During the pandemic, many universities have chosen for online proctoring. Although some earlier examples suggest that online proctoring may reduce cheating, the potential side-effects of proctoring are largely unknown. Objectives: Therefore, this study aims to identify the effects of proctoring on students' self-reported temptation to cheat and potentially undesirable side-effects, including test anxiety, perceived exam difficulty, and performance. In addition, we examine which contextual and student characteristics affect test anxiety during online exams. Methods: For this, we collected four waves of survey data throughout a year of teaching during the pandemic at one faculty of a Dutch university, resulting in a total sample of 1760 students within 105 courses. Results and Conclusions: Multi-level analyses showed that while proctoring had no effect on the temptation to cheat, exam difficulty or performance, students reported higher levels of test anxiety. Some learning strategies, internet literacy, access to a reliable technology and a dedicated study space as well as gender and financial stress affect their test anxiety. To conclude, the decision to use online proctoring needs to consider the undesirable side-effect on test anxiety. We discuss practical implications for university administrators, educational designers and teachers to reduce test anxiety.