Place chicken breasts in the bottom of slow cooker. Sprinkle with salt and pepper.
Turn slow cooker to HIGH and cook for 3 - 4 hours, until chicken pulls apart easily with a fork and reaches an internal temperature of 165°F on meat thermometer.
Remove chicken to a large platter to cool slightly. Using two forks, shred meat into small pieces.
Cover and refrigerate up to 3 days. Freeze in labeled airtight containers or freezer bags for up to 3 months.