The comedian and show host is in the country as part of activities to mark the Year of Return.
This year is exactly 400 years since the first black slaves landed in Jamestown Virginia in the US.
"This was real pain I felt going back to Ghana’s slave castles...I could feel my ancestors on me...," Harvey posted on Instagram.
He added: "Powerful beyond words that I can explain. I encourage as many of you as possible to go HOME for your ancestors. Their strength is in each of us and we must honor their ultimate sacrifice in all that we do."