The Ferrari chairman compared Raikkonen to retired triple world champion Niki Lauda, who took a two-year break from Formula One in 1980/81 and then returned to win another championship.
Raikkonen, world champion in 2007, left Ferrari at the end of 2009 - departing a year early with a hefty payoff to make way for Alonso - and returned with Lotus in 2012 as a title contender again after two years out.
Ferrari announced last week he had signed a two year deal for 2014/15.
"We are not so masochistic as to sign a driver without telling Alonso," Montezemolo, who worked with Lauda when the Austrian won two titles for Ferrari in the 1970s, told the Gazzetta dello Sport newspaper in a wide-ranging interview. "Fernando was always kept up to date about the choice of Raikkonen..."
The pairing of two champions is a big change for Ferrari but Montezemolo, who has spoken in the past about not wanting "two roosters in the same hen house", said the alternative of a young driver was too risky in a season like 2014 with major rule changes including a new V6 engine.
"Raikkonen is the strongest of all, with Alonso, (Sebastian) Vettel and (Lewis) Hamilton," he added. "And Alonso is the first to be satisfied with his arrival."
Alonso made clear before Raikkonen's return to Ferrari was announced this month that he would be happy for Brazilian team mate Felipa Massa to stay on.
The Spaniard's relations with the team have gone through a rough patch in recent months but Montezemolo compared Alonso to a soccer player angry at being substituted during a match and making his views clear.
Montezemolo said talks with Raikkonen began 10 days before the Italian Grand Prix at Monza on Sept. 8.
"Raikkonen's is the same case as Lauda's," he said, although Lauda won his third title with McLaren and not Ferrari in 1984. "Niki also at a certain point said 'enough' because he could not go on...the break has done him good, he's returned on top form, he's won and finished so many races.
"I wanted a driver who would not make me regret Massa (leaving). I'm asking Kimi for wins, consistency, podiums. Alonso will be the first to benefit," he added.
Massa has been quoted recently in the Brazilian media as saying he would put himself first, rather than supporting Alonso, for the remaining seven races but Montezemolo doubted that.
"Felipe is a great lad and a splendid person," he said. "They say he won't help Fernando? Nonsense! Of course he will, lending a hand to us for the constructors' title and to Alonso for the drivers'."
Alonso is second overall, 53 points behind Red Bull's triple champion Vettel, going into Sunday's Singapore Grand Prix. Massa is 143 adrift of the German.