Light affects all aspects of plant growth and development from seed germination to senescence. While there has been intensive investigation of the effects of blue and red light on development and tropisms, much less is known about the specific effects of green light exposure in plants. Several recent studies demonstrate that monochromatic green light has a number of physiological effects including antagonizing light-mediated growth inhibition in hypocotyls and reversing blue-light-induced stomatal opening. In this paper, we report on the effects of green light pulses on phototropism in both light- and dark-grown seedlings of Arabidopsis thaliana. Green light had no effect on either red-light or blue-light-based phototropism in roots. However, in hypocotyls of dark-grown seedlings, pulses of green light significantly reduced blue-light positive phototropism while the growth rate was increased. In contrast, in hypocotyls of light-grown seedlings, green pulses significantly increased positive phototropic curvature while there was no significant effect on growth rate. The observed effects of green light may occur by perception through the phytochromes or via a novel undiscovered green light receptor. Taken together, these results suggest that care should be taken when green illumination is used as a “safe” light in studies of plant development. While green light effects may be more subtle compared to red and blue effects, monochromatic green illumination can influence the growth and development of seedlings.