In a medium bowl, combine the sliced chicken breast with olive oil, ground cumin, smoked paprika, chili powder, garlic powder, salt, and black pepper. Mix well to coat the chicken evenly with the spices.
Heat a large non-stick skillet over medium-high heat. Add the seasoned chicken slices and cook for 5-7 minutes, stirring occasionally, until the chicken is cooked through and lightly browned. Remove the chicken from the skillet and set aside.
In the same skillet, add the sliced red, green, and yellow bell peppers along with the sliced onion. Sauté for 5-7 minutes until the vegetables are tender but still slightly crisp.
Return the cooked chicken to the skillet with the vegetables and stir to combine. Cook for an additional 1-2 minutes to heat everything through.
Warm the whole wheat tortillas in a dry skillet or microwave for 20 seconds until pliable.
To assemble the fajitas, divide the chicken and vegetable mixture evenly among the tortillas.
Garnish each fajita with chopped fresh cilantro and serve with lime wedges on the side for squeezing over the top.