The Tudors have been looking for a new boss since Dean Brennan departed Vauxhall Road last month.
He moved to title chasing Billericay Town and the search has been on since then.
Jordan Parkes has been in caretaker charge of the team as they sourced a replacement but results have taken a turn for the worse.
Now they have the man who the club hope can turn their National League South fortunes around and he wasn't hanging around on Saturday afternoon.
Deeney moves to the Tudors from divisional rivals Oxford City, where he was assistant manager.
He has been keen to try his hand being a number one and says he is “very excited” about the challenge ahead of him.
It was a difficult start at Bath City but he came through it with flying colours.
Hemel won 1-0 at Twerton Park thanks to a goal as Steve Cawley came up trumps 15 minutes from time.