Edmondson attacked with 20 kilometres to go and was joined by fellow South Australian and training partner, Chris Harper (Bennelong SwissWellness).
The pair held off a select peloton until the final few hundred metres, where a galloping Jay McCarthy (Bora-Hansgrohe) finished in between the two mates to steal silver off Harper.
An emotional Edmondson said his role was to be a loyal team-mate but everything seemed to go his way.
"I'm absolutely speechless," Edmondson said. "I came here trying to do teamwork and aaahh...sorry...this means a lot to me.
"This is just a fairy tale. To come away with green and gold is a dream. I'm absolutely stoked, everything seemed to go by way and I managed to get there to the line. Awesome feeling."
A world champion track star in his own right, Edmondson is still somewhat an emerging star on the WorldTour.
"I've been chipping away doing small things here and there (on the road). Today, it's hard everyone wants to win.
"I'm trying to hold back the tears. An awful lot goes into this. Everyone makes so many commitments. This isn't just for me, but for everyone."
Edmondson said that although he and Harper were good mates, team loyalty always won out.
"He's the one pushing me. We're such good friends off the bike but you have to look after your team mates. There were a lot of words going back and forth, but it's my day today, there'll be plenty of opportunities for Chris Harper."
The pair caught Supercross rider Troy Herfoss, who also showed his talent without a motor, riding off the front solo for 20 kilometres.
Edmondson's teammate Caleb Ewan finished fourth, ably towed around the last lap by Cam Meyer should Edmondson's move falter. Richie Porte, exhausted by several moves on the final lap, was the last of the chasing group of 14 riders at the finish.
As always, it was a race of attrition and there were only 38 finishers from about 140 starters.
Porte's new teammate Simon Gerrans set an aggressive pace just after halfway at the front of the main group, rapidly bringing down the seven minute time gap to the initial lead group of eight riders and shredding the peloton.
Gerrans swung off with about 40km left, his work done.
It is the first time in four years that Mitchelton-Scott has won the coveted men's elite road title. And on a day of harsh contrasts for the team, Luke Durbridge crashed inside the last 15km and suffered a broken collarbone and concussion, ruling him out for the rest of the Australian season.
The layoff will also interrupt his buildup for the European spring classics, where he will be a team leader.
In the race of attrition and there were only 38 finishers from about 114 starters.
