We consider the use of demand response to address phase unbalance in a distribution grid. At present this problem is addressed by modifying the topology of the grid, but this has limited flexibility because it can only be done once or twice a year. We propose to use demand response to minimize phase unbalance on a 15-minute basis. Because phase unbalance is difficult to estimate analytically, we assess it using the OpenDSS distribution system simulator and we optimize using a black-box optimization algorithm. Our approach reduces the phase imbalance by up to 50% on the IEEE 123-bus feeder.