The 35-year-old Hoops captain will relocate to Pittodrie in a player-coach role under new boss Stephen Glass in the summer after 14 success-laden years at Celtic Park where he won 22 trophies.
The Parkhead club are currently in search of a new manager after Neil Lennon resigned in February with assistant John Kennedy in temporary charge. Chief executive Peter Lawwell is also leaving at the end of the season to be replaced by Dominic McKay, who is moving from Scottish Rugby, and on Wednesday night Celtic announced that Nick Hammond, head of football operations, resigned to "pursue new opportunities".
Ahead of the Scottish Cup third-round tie against League One side Falkirk on Saturday night, midfielder Brown said: "I got offered another year at Celtic. It is a hard situation just now because it would have to be sitting waiting to the end of the season to see who comes in.
"For me, to have that fresh start with someone I know, trust and respect fully, and maybe sitting in at Celtic to the end of the season not sure what to do or who is coming in - I think that played on my mind as well.
"It will be a sad time when I do leave but it has been fantastic, I have enjoyed every moment, winning trophies, winning games, playing in front of our fantastic fans."
Asked if he had considered staying on to help with the transition at the Parkhead club, Brown said: "That was always in the back of my mind as well.
"I have to look at the selfish point as well. Aberdeen offered a two year-deal and it was an offer I couldn't turn down."
Brown aims to win over any Aberdeen fans who may be less than happy with his arrival.
The former Hibernian player has had a series of run-ins with Dons players past and present, such as Graeme Shinnie and Shay Logan, and wound up the Red Army fans.
He said: "I had to win over the fans at Easter Road coming through as a young lad. I had to win over the fans at Celtic as well and I am sure there will still be some who don't like the way I play but that's part and parcel of football, you can't please everybody.
"Wherever I go, whoever I play for, I will give 110 percent on the park, give a lot on the training ground and I will always do what is best for the football club."
He added: "I have had 14 fantastic years at this club and enjoyed every moment of it, even some when we have been getting beat as well.
"It has been a wonderful career for myself, I have enjoyed the moments with the fans and it is just a pity that I can't share the last five or six games with them in the stadium because they have been part of my journey.
"It will be emotional at the last game of the season but it will be a fresh start for me.
"I am really looking forward to the challenge next season, helping out with Stephen and the backroom staff, but also playing as well."