Future World Champion Lewis Hamilton drove the MP4-21 in his first official Formula One test in September, 2006 prior to joining McLaren for 2007.

[3] The MP4-21 was designed by Adrian Newey, Paddy Lowe, Tim Goss, Mike Coughlan and Peter Prodromou.

In addition, the utilisation of the new V8 specification engines meant that the side air intakes were reduced in size, therefore making aerodynamic benefits.

[13] de La Rosa would score a career best second place at the 2006 Hungarian Grand Prix driving the MP4-21.

[15][16] Following the conclusion of the season, former driver and two time World Champion Mika Hakkinen tested the MP4-21 with a view to an F1 return.

[17][18] An MP4-21 showcar is displayed at The National Motor Museum in Beaulieu, although now painted in Jenson Button's 2010 livery.

[21] Chassis 3, driven by Montoya in the first three Grands Prix of the season and later tested by Hamilton, sold for £2 million in early 2025.