The defender, a Millwall great with nearly 350 appearances, will step up to help manager Neil Smith as a first team coach.
The 35-year-old will still be an active member of the team but has now switched his attention to what happens after he retires.
Explaining about the next chapter in his career, Dunne told Bromley’s website: “I’m really pleased. I’ve been here 21 months now and enjoyed every single moment of it. Neil and Mark took me in and I had to earn their trust and since I’ve come in I have learnt a lot from them.
“When I came here I wanted success, and the Club tasted success last year. We have personal targets we want to achieve and targets as a Club as well.
“We want to kick on, it’s the start of something here where we can go on and achieve things, and I’m very proud to be a part of that.”
Manager Smith said: Young players in particular need experience around them and Alan gives them that.
“He’s a been a credit to himself fitness wise, so I don’t see there being any problems if I have to call on him to play.”