Sullivan was accused of sexually exploitative and predatory behaviour by seven women during a joint investigation by the BBC and Britain's The Times newspaper.
The 77-year-old businessman quit as joint chair of London football club West Ham before the investigation was broadcast in June to fight what he said were "false allegations" about his private life.
But Sullivan, who built a business empire from owning pornographic magazines, remains West Ham's largest shareholder.
London Stadium issued a statement on Tuesday saying safeguarding issues were behind their advice, but Sullivan opted to attend the first-round match against Portsmouth, with the Hammers, relegated from the Premier League last season, beating their second-tier rivals 3-1.
London Stadium said: "Following media reports at the end of the season regarding a safeguarding matter being managed by the club, London Stadium sought further information to ensure it could fulfil its own safeguarding responsibilities.
"Based on the information provided by the club, we understand the matter was investigated and that the club does not consider there to be an ongoing safeguarding risk associated with Mr Sullivan attending the stadium.
"However, given the potential for demonstrations and anti-social behaviour by some spectators, we have recommended to the club that he does not attend.
"We have also requested advance notice of any planned attendance so that appropriate safety and operational measures can be put in place."
There were no reports of any unrest among fans before or after the game kicked off.