Vunipola liked a post on Australian rugby star Israel Folau's page apparently warning homosexuals they face hell if they do not repent.
England Rugby released a statement on Tuesday morning, claiming Vunipola showed "genuine regret".
After a meeting between Rugby Football Union (RFU) and Vunipola, the Saracens forward was issued with a formal warning under RFU rule 5.12 for "conduct prejudicial to the interests of the union or the game".
The statement reads: "The warning will be retained on his disciplinary record for a period of five years and may be taken into account in future disciplinary proceedings.
"During the meeting the player expressed genuine regret at his public comments and understood that he had caused hurt and offence as a result of his actions.
"He has been reminded of his responsibilities as an England player and as an ambassador for the game, which values inclusivity and respect"
What did Billy Vunipola do?
In an apparent show of support to his fellow Christian, Vunipola states that "Man was made for woman to pro create that was the goal no?"
However, England's first choice number eight adds that "I don't HATE anyone".
At the time of writing, Vunipola's post has still not been deleted.