Size matters when determining the correct Instant Pot chicken breast cook time. Get the perfect high pressure cook time below, always follow up with a 10 minute natural release for each. SMALL 6 oz organic chicken breasts6 minutes fresh, 10 minutes frozenMEDIUM 8 oz grocery store chicken breast 7 minutes fresh, 11 minutes frozenLARGE 10 oz bulk chicken breasts9 minutes fresh, 12 minutes frozen*If using frozen chicken breast, make sure to separate them, the chicken still needs to be in a single layer.