The Benin international's family have struggled to settle in the north-east and the Black Cats' boss faces a battle to keep the creative midfielder at the Stadium of Light
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.”
The Ulsterman also admitted that Sessegnon wouldn’t be short of suitors if he decided to leave, but insisted the midfielder has not hinted he wants to leave.
“For normal reasons we should do it [keep him] and for very obvious reasons, because he is going to attract an awful lot of attention from big clubs,” he continued.
“I'm hopeful but never confident, particularly when it comes to players. He has not mentioned anything. I haven't had a word from his agent yet.
"I believe his name will be bandied around significantly, we'd hate to lose him at this point, we really would. If it's because of homesickness it is something we would have to look at.”
O'Neill is keen to avoid similar problems with other players, claiming that those moving from other areas of Britain are also affected.
The 60-year-old explained: “It is not just appertaining to foreign players, but players moving from one side of the country to the other - it seems crazy, but they have a bit of difficulty and some part of their family don't want to move.
“That is something, particularly with Sessegnon, we really need to have a look at.”