The actress has been forced to leave her Broadway show after being diagnosed with the disease, reports Extra.
Posey, 40, who starred in several films including Best in Show and Party Girl, will not be taking the stage in the production of This.
Lyme disease, which is transmitted by ticks carrying a particular bacteria, can lead to severe problems in the brain, heart, nerves and joints if left unattended.
A replacement for Posey in This, which opens on November 6, has not been named.