A system and method of controlling a low-voltage DC/DC converter for an electric vehicle that include a battery sensor that senses information regarding a low-voltage battery during a stop of the electric vehicle for each first period when the electric vehicle stops and a controller that operates a low-voltage DC/DC converter to charge the low-voltage battery for a predefined time when an error occurs in the battery sensor. In addition, the controller determines a charge time of the low-voltage battery based on first SOC values of the information regarding the low-voltage battery sensed for each first period when no error in the battery sensor is detected and operates the low-voltage DC/DC converter for the determined charge time to charge the low-voltage battery.