Heat the vegetable oil in a large skillet or wok over medium-high heat. Add the chicken pieces and season with salt and pepper. Cook for about 5-7 minutes until the chicken is browned and cooked through. Remove the chicken from the skillet and set aside.
In the same skillet, add the sliced bell peppers and snap peas. Stir-fry for 3-4 minutes until the vegetables are tender-crisp.
Add the minced garlic and ginger to the skillet and stir-fry for an additional minute until fragrant.
Return the cooked chicken to the skillet. Add the diced mango, soy sauce, honey, and rice vinegar. Stir to combine and cook for 2-3 minutes until heated through.
Stir in the cornstarch mixture to thicken the sauce. Cook for another minute until the sauce has thickened.
Serve the mango chicken stir-fry over cooked rice or quinoa.