Mackay-Steven had to be pulled from Glasgow’s River Kelvin by firefighters after a late-night drama last month.
The 26-year-old former Celtic forward took the plunge after leaving a nearby nightclub as he celebrated his side’s 4-3 victory over Partick Thistle.
He had to be treated in hospital for hypothermia after reportedly spending a hour in the bitterly cold water but was well enough to return home hours later.
McInnes has held discussions with the player and says that is now the end of the matter.
However, the Pittodrie boss has warned Mackay-Steven he must never repeat those alcohol-fuelled antics again.
Speaking to RedTV, the Dons manager said: “I’ve spoken to Gary and it was totally out of character for him.
“I think it’s a reminder of the spotlight the players are under, a reminder of the restraint and discipline that’s required.
“I’ve no problem with players relaxing and switching off. There’s no better time to relax and switch off when there’s two weeks before your next game.
“But there is no place for a footballer to be as drunk as he was and then the consequences of what happened.
“It’s bizarre circumstances but we’re here to support Gary. However, it’s also a reminder to him and everybody else of the responsibly to make sure there is that restraint and discipline at all times.
“By all means have a drink - but make sure you’re in control of the situation.
“We’ve addressed it now. We don’t expect it to be an issue going forward with him or any other of my players.
“It could have been far more problematic for him but thankfully he is back with us. He is embarrassed as you would expect and feels he has let people down but we are here to support him.
“He’s a good lad with so much to offer. It’s all about learning as nobody is perfect.”