The creative midfielder’s family have failed to adjust to life on Wearside and O’Neill fears that he could be forced to leave the Stadium of Light as a result.
But the Black Cats' boss expects the club do its utmost in an effort to keep the 27-year-old, who has been instrumental in the Mackems' rise up the Premier League table.
He said: "We wouldn't want to lose Sessegnon because of homesickness.
“His family concerns over there are something we will really have to look at, particularly now.
“I think the club has got a good reputation for trying to help. We will do everything we can, put it this way.
“We have someone here at the football club that is in constant touch with Sess. We have given him a little bit of time to go and see his family.”