The McLaren team owner Ron Dennis asked Alonso in Brazil in October 2005 whether he would like to drive for his team in the future after Alonso expressed interest in doing so.
Alonso and Dennis met secretly in Japan, signing a three-year contract three weeks later.
Alonso's family, lawyers and his manager Luis Garcia Abad negotiated; he was eager to inform Flavio Briatore about the deal in person but could not do so due to a scheduling conflict.
The news was made public on 19 December 2005.
Alonso told McLaren senior personnel before the 2006 German Grand Prix he was dissatisfied with the relationship between himself and Briatore, with Dennis and Garcia discussing Alonso joining McLaren in a mid-season swap, before concurring an agreement was unfeasible.

His contract with Renault was due to expire on 31 December 2006; Alonso was not granted an early release for sponsorship reasons.
After McLaren did not approach Briatore about an early release of Alonso to them, he and Renault allowed Alonso to acclimatise with McLaren.
Alonso drove a MP4-21 car at a test session at the Circuito de Jerez after pleading with Briatore to reach a compromise after Dennis could not do so.
McLaren were initially concerned that Alonso's aggressive driving style would not suit their car because they believed Renault had built themselves around him.
He had two seat fittings in the MP4-22 car at the McLaren Technology Centre, the team's Woking headquarters, between December 2006 and January 2007.
McLaren reportedly paid Alonso £60 million.
He said his objective was to win the world championship and felt McLaren's switch from Michelin to Bridgestone tyres would help him.

That year, Alonso challenged his teammate Lewis Hamilton and Ferrari's Kimi Räikkönen for the championship.
He took four race victories in Malaysia, Monaco, Europe and Italy and led the points standings after the Malaysia round before Hamilton took it from him.
Before the season-ending Brazilian Grand Prix, he had 103 points in the championship to Räikkonen's 100 and Hamilton's 107.
Alonso needed to win the race and for Hamilton to finish third to win the championship.
He finished third in the race for third overall with 109 points.
He had the same number of points as Hamilton; the tie was broken on count-back, Alonso had one less second-place finish than Hamilton.
The McLaren team owner Ron Dennis asked Alonso in Brazil in October 2005 whether he would like to drive for his team in the future after Alonso expressed interest in doing so. Alonso and Dennis met secretly in Japan, signing a three-year contract three weeks later. Alonso's family, lawyers and his manager Luis Garcia Abad negotiated; he was eager to inform Flavio Briatore about the deal in person but could not do so due to a scheduling conflict. The news was made public on 19 December 2005. Alonso told McLaren senior personnel before the 2006 German Grand Prix he was dissatisfied with the relationship between himself and Briatore, with Dennis and Garcia discussing Alonso joining McLaren in a mid-season swap, before concurring an agreement was unfeasible.
His contract with Renault was due to expire on 31 December 2006; Alonso was not granted an early release for sponsorship reasons. After McLaren did not approach Briatore about an early release of Alonso to them, he and Renault allowed Alonso to acclimatise with McLaren. Alonso drove a MP4-21 car at a test session at the Circuito de Jerez after pleading with Briatore to reach a compromise after Dennis could not do so. McLaren were initially concerned that Alonso's aggressive driving style would not suit their car because they believed Renault had built themselves around him. He had two seat fittings in the MP4-22 car at the McLaren Technology Centre, the team's Woking headquarters, between December 2006 and January 2007. McLaren reportedly paid Alonso £60 million. He said his objective was to win the world championship and felt McLaren's switch from Michelin to Bridgestone tyres would help him.
That year, Alonso challenged his teammate Lewis Hamilton and Ferrari's Kimi Räikkönen for the championship. He took four race victories in Malaysia, Monaco, Europe and Italy and led the points standings after the Malaysia round before Hamilton took it from him. Before the season-ending Brazilian Grand Prix, he had 103 points in the championship to Räikkonen's 100 and Hamilton's 107. Alonso needed to win the race and for Hamilton to finish third to win the championship. He finished third in the race for third overall with 109 points. He had the same number of points as Hamilton; the tie was broken on count-back, Alonso had one less second-place finish than Hamilton.
Motor racing career of Fernando Alonso