Rational number learning can cause frustration and negative emotions for elementary school students. Fraction Ball, a play-based math intervention, allows students to actively learn rational numbers through engaging and interactive activities. Based on a cluster-randomized trial with 16 teachers and 360 students, our pre-registered analyses showed moderate positive impacts of Fraction Ball on overall students' self-reported math-related emotions. Exploratory analyses indicated that students with higher negative emotions at pretest showed larger experimental impacts on decreasing negative emotions at posttest. Finally, we found that Fraction Ball evidenced no trade-off between rational number learning and emotional outcomes at the classroom block level, indicating that positive learning gains in rational number skills were associated with increases in positive emotions and decreases in negative emotions.