Aim/Purpose: We aimed to investigate the circumstances under which Kahoot! (a Game-based Student Response System (GSRS)) increases junior and senior Information Science university students’ learning and knowledge retention beyond that of traditional teaching methods. We also explored whether the positive learning impacts of Kahoot! vary as a function of student subject knowledge (i.e., junior vs senior students). Background: The effectiveness of game-based student response systems (GSRSs) as learning tools in the classroom remains unclear, given inconsistent findings across educational research. Kahoot! enhances secondary and tertiary students’ attention and motivation during class, but its effectiveness on learning and retention of course knowledge may vary depending on situational and individual factors. In New Zealand universities, students spend three years studying towards a Bachelor’s degree, majoring in subject(s) of their choice. By the end of their third year of study, students are eligible to graduate with a sound knowledge of their chosen major. Thus, first-year students (referred to as “junior students”) and third-year students (“senior students”) may differ in terms of their learning styles and their ability and willingness to integrate Kahoot! use into their course work and revision. It is hypothesised that differences in subject knowledge between junior versus senior students will influence the perceived effectiveness of Kahoot!. Methodology: Thirteen first-year (junior) and fourteen third-year (senior) Information Science students (total n = 27), who used Kahoot! in seven lectures (for 30 minutes per lecture) were interviewed about their perception of Kahoot!’s effectiveness. We conducted a mixed-methods case study of students’ interview transcripts, demographic records and student scores, where thematic (content) analysis was used to analyse interview responses. Then, we quantified themes for a one-way ANCOVA, with student subject knowledge predicting Kahoot!’s effectiveness, when controlling for students’ duration of tertiary study and study habits (i.e., hours dedicated to course work per week) as potential confounders. Contribution: This study addresses the conflict in existing literature around whether GSRSs improve student learning beyond traditional teaching methods. To our knowledge, this is the first study that shows GSRSs (namely Kahoot!) use improves, or at least, supplements tertiary students’ learning and knowledge retention of lecture content. This study also reveals how student characteristics (i.e., accumulated tertiary experience) and their subject knowledge influence the effectiveness of Kahoot! as a learning tool. Findings: Kahoot!’s use increased students’ learning and knowledge retention, among other positive impacts (e.g., attention and engagement). However, the perceived learning impact of Kahoot! was greater for senior students. Senior students found Kahoot! more useful for learning new knowledge and revising previously acquired knowledge. On the other hand, while junior students also experienced positive learning impacts using Kahoot!, they reported concerns regarding limited and shallow content coverage, and the time-consuming and distracting nature of the platform. Recommendations for Practitioners: Educators should take care to ensure GSRSs are appropriately implemented to support rather than replace traditional teaching methods (e.g., “chalk and talk” style presentations, PowerPoint use). In addition, lecturers using GSRSs should clearly inform students about the examinable content and their expectations for performance in formal assessments. Recommendation for Researchers: The positive impact of Kahoot! use on students’ learning and knowledge retention may be due to stronger interactions and engagement during class. Researchers should more closely explore how student-lecturer interactions and in-depth discussions following GSRS use influence learning. Thus, there is a need to re-evaluate Malone’s (1980) intrinsic motivation theory in relation to the “interactive” or “enjoyability” components experienced during Kahoot! use. Impact on Society: The positive impacts of Kahoot! use on student learning vary for junior and senior students. However, our findings indicate that both cohorts of students benefit from 15-minute Kahoot! sessions at the end of a lecture or course unit, allowing them to test their knowledge and revise* previously taught material. Kahoot! provides a comfortable platform that allows students to ask and answer questions without embarrassment. More experienced students can also evaluate their learning by creating their own Kahoot! quizzes and providing feedback to the lecturers. Overall, Kahoot! use could have a positive impact on teaching and learning globally. Future Research: Beyond the recommendation for researchers above, future research should explore how differences in lecturers’ teaching styles and students’ self-regulation of learning impact Kahoot!’s effectiveness as a learning tool.