Yeast cells polarize by projecting up mating pheromone gradients, a classic cell polarity behavior. However, these chemical gradients may shift direction. We examined how yeast cells sense and respond to a 180(o) switch in the direction of microfluidically-generated pheromone gradients. We identified two behaviors: at low concentrations of α-factor, the initial projection grew by bending, whereas at high concentrations, cells formed a second projection toward the new source. Mutations that increased heterotrimeric G-protein activity expanded the bending growth morphology to high concentrations; mutations that increased Cdc42 activity resulted in second projections at low concentrations. Gradient sensing projection bending required interaction between Gβγ and Cdc24, whereas gradient non-sensing projection extension was stimulated by Bem1 and hyper-activated Cdc42. Interestingly, a mutation in Gα affected both bending and extension. Finally, we searched for a genetic perturbation that would exhibit both behaviors; overexpression of the formin Bni1, a component of the polarisome, made both bending growth projections and second projections at low and high α-factor concentrations suggesting a role for Bni1 downstream of the heterotrimeric G-protein and Cdc42 during gradient sensing and response. Thus, we demonstrated that G-proteins modulate in a ligand-dependent manner two fundamental cell polarity behaviors in response to gradient directional change.