Introduction: We routinely study how the quantity of light affects rates of plant photosynthesis. However, what happens to photosynthesis when we change the angle of light? A growing body of research has demonstrated changes in leaf photosynthesis and net ecosystem exchange in diffuse light conditions caused by clouds or other aerosols. However, our understanding of the effects of diffuse light on physiological processes and the concomitant effects on growth and yield remain limited. Methods: We compared the physiology, growth and yield of tomatoes (Solanum lycopersicum) grown in direct compared to diffuse light conditions. Diffuse light conditions (ca. 50-60% diffuse) were created by a painted glass panel that leads to diffusion of light, but does not significantly reduce the quantity of light. Results: We observed significant differences in photosynthetic function, including water-use efficiency, of plants in diffuse light as compared to direct light conditions. However, there was increased leaf cupping in plants grown in direct light, which may be due to higher temperatures (ca. 3-5 °C) in that treatment. We also observed no differences in initial plant growth (height, leaf number, and stem diameter); however, fruiting in the diffuse light conditions was higher than in direct light conditions. Discussion: Diffuse light conditions may have their greatest impact on plant structure and function by increasing flowering and fruit production. This effect may be mediated not by the light quality, but in this case by the temperature change induced by diffusing the light. As the climate warms, these results suggest that simple modifications to greenhouse structure may benefit fruit yield for key crops.