Background Classroom lighting, usually bright fluorescent light, can significantly influence the learning environment and emotions of students. Objective To assess the emotional impact of classroom lighting on students during an academic year. Methods This study used an ABAB withdrawal research design in the following manner: in phase A, the baseline condition, classroom lighting was provided by conventional overhead white fluorescent classroom lights; in phase B, the intervention condition, the conventional overhead white fluorescent classroom lights were covered with fabric filters (thin, translucent, creamy-colored plastic sheets) that were attached to the lighting fixture frame with magnetic discs. The filters produced softer light in the classroom than the fluorescent lights. Each phase lasted for at least 2 weeks. During each phase, students rated 18 pairs of words from the Mehrabian and Russell pleasure, arousal, and dominance semantic differential scale at least four times to assess the emotional impact of the lighting conditions. Results For all three emotional behaviors, the mean score of the filtered fluorescent light phase was significantly greater than the mean score of the baseline unfiltered fluorescent lighting phase, indicating more positive emotional responses. Students also noted they experienced fewer headaches and found it easier to see the whiteboard at the front of the classroom when the light filters were in place. Conclusion The light filters exerted a positive impact on the students’ emotions. Students preferred the filtered lighting to fluorescent lighting. This study supports the installation of filters over fluorescent lights in a college classroom.