Add the chicken and ¾ cup barbecue sauce to a 6-quart slow cooker, stirring to combine.
Cover and cook on high for 3-4 hours, or low for 5-6, or until the chicken is cooked through and shreds easily with a fork.
Remove the chicken to a cutting board. Chop into pieces or shred with two forks. Drain about half of the remaining liquid from the slow cooker and discard or save for another use.
Add the shredded chicken back to the slow cooker along with the remaining ¾ cup barbecue sauce, stirring to combine.
Serve the pulled chicken piled into toasted buns and additional sauce if desired.
Nutrition information calculated using chicken breasts and without the optional serving suggestions listed above. Sugar content will depend on the specific BBQ sauce used.