The Brazilian was contracted to Atletico between 1997 and 2002, although he spent much of it either injured or on loan elsewhere. He nevertheless retains affection for the Vicente Calderon club and feels they have the ability to land their first Champions League crown this weekend against Cristiano Ronaldo and Co.
He told Omnisport: "If we see the individuals, Real Madrid have a better team than Atletico and have a player [Ronaldo] who can make a difference on the game at any time.
"But, with Atletico Madrid, we can see a group, maybe even stronger than Real Madrid, especially with the team spirit that they have, knocking out two teams, which in my opinion, are the two bests teams in the world, Barcelona and Bayern Munich.
"So for me Atletico has great momentum to go to the final and beat Real Madrid."
Atletico's game is based largely around a strong defensive structure, but Juninho thinks they will have to show more at the other end of the field if they want to beat Madrid, having lost 4-1 to them in the 2014 showdown that went to extra time.
He added: "This game is a rematch of the final two years ago, in which Atletico Madrid had pretty much the game in their hand, but in the last few minutes Real turned the game and maybe that has helped Simeone to learn because you can't defend for 90 minutes.
"I think, at some point, Atletico will have to attack as well."
Juninho feels the two teams mirror the personalities of their coaches – Atletico's Simeone and Madrid's Zinedine Zidane.
"I think Simeone has more experience than Zidane. Zidane just started and is already having success, so needless to say the knowledge of football he has. But in terms of training, I think Simeone has a bit more experience than Zidane," he said.
"They have different styles, I think you can see on the pitch that each team has the face of the coach, Real Madrid playing more offensive and Atletico playing more defensively, looking for counter-attacks, it has the face of Simeone."