Public speaking is important in the sciences, but poor quality presentations are common, as are high rates of public speaking anxiety. In this work we explore the use of a mobile humanoid robot as a co-presenter that can share the stage with a scientist giving an oral presentation. We conducted a within-subjects experiment comparing presentations given with and without the robot and impacts on public speaking anxiety and speaker confidence. We found that participants reported significantly greater confidence and lower public speaking anxiety when co-presenting with the robot, compared to when they presented on their own, without the robot. Audiences accepted scientific presentations given with the robot, rating these presen-tations significantly greater than neutral on presentation quality.