McLaren test driver Pedro de la Rosa was given the honour of being the first person to put their 2006 car through its paces, at testing in Barcelona.
De la Rosa in the new McLaren
The Spaniard was impressed with the new Mercedes-powered model, which uses a 2.4-litre V8 engine.
"It feels good initially but it is of course too early to really understand its potential, and we need to put a lot more laps on it," he said.
"Our focus will be to familarise ourselves with the car and the engine."
McLaren, who just missed out on both the drivers and constructors world titles last season, have not won a world championship for seven years.
De la Rosa added: "We have around 20 days of on-track running before the cars leave for Bahrain on 3 March."
Chief executive Martin Whitmarsh is promising more improvements before the 2006 season gets under way on 12 March.
"The anticipation within the team as to how competitive the new car will be is great, particularly given the pace of our 2005 racer and the level of work that has been put into this project.
"However these are early days, we have a comprehensive programme to complete with the car over the next few weeks.
"This will mean hard and dedicated work from the whole team supported by our technology partners and official suppliers, including an aggressive schedule of upgrades to come online before Bahrain."