In the base of an instant pot or pressure cooker, combine the chicken and basil pesto. Make sure the chicken is coated well. Secure the lid onto the pressure cooker. Turn on instant pot, select "Pressure Cook" setting, set to "high pressure" for 18-20 minutes*, and start.
Once the timer has expired and the chicken has finished cooking, allow the pressure to release naturally. The chicken should temp at 165 degrees F. once done. Allow to cool slightly, serve sliced or whole, spoon any extra pesto over top. Leftover chicken will keep in an airtight container in the fridge for 3-4 days.
Notes
*If the chicken breasts are thick, pound them slightly to thin them out before cooking.