Heat olive oil in a large deep skillet or pot over medium-high heat.
Add the chicken pieces to the pot and season with salt and black pepper. Cook for 5-6 minutes, stirring occasionally, until the chicken is browned and cooked through. Remove the chicken from the pot and set aside.
In the same pot, add the chopped onion and cook for 3-4 minutes until softened.
Add the minced garlic and cook for 30 seconds until fragrant.
Add the orzo pasta to the pot and stir to coat it with the oil, onion, and garlic mixture.
Pour in the chicken broth and bring the mixture to a boil.
Reduce heat to medium-low, cover, and simmer for 10-12 minutes, stirring occasionally, until the orzo is tender and most of the liquid is absorbed.
Return the cooked chicken to the pot and stir in the basil pesto and grated Parmesan cheese until well combined and heated through.
Taste and adjust seasoning with additional salt and black pepper if needed.
Serve hot, garnished with fresh basil leaves.