Place the chicken breasts in the bottom of the crockpot.
Sprinkle the taco seasoning over the chicken.
Top with the diced onion, jalapeno, garlic, salsa, and then pour tomatoes oer the top with the undrained green chilies.
Cover and cook on low for 6-8 hours.
Shred the chicken with forks and mix well.
Serve on tortillas with your favorite taco toppings.