Place the chicken breasts in the crockpot.
Sprinkle the taco seasoning over the chicken.
Add the chopped onion and minced garlic on top.
Pour in the chicken broth and diced tomatoes.
Season with salt and pepper as desired.
Cover and cook on low for 6-8 hours or high for 3-4 hours.
Once cooked, shred the chicken using two forks.
Stir the shredded chicken back into the juices.
Warm the tortillas in a pan or microwave.
Serve the shredded chicken in tortillas with your favorite toppings.