Alonso missed the Monaco Grand Prix to race at Indianapolis this year but that was fully sanctioned by the team and Honda due to their dismal performance in the Formula One championship.
"Today's announcement shows that he's fully committed to racing and winning as a McLaren driver, and, while we've often shared his frustrations over the past few years, we now feel that we can deliver on our promise to give him a competitive auto next season", added Boullier.
He has a long-term goal of becoming only the second driver to complete the Triple Crown - winning the Monaco Grand Prix, Le Mans and the Indy500.
"For the Indy 500 it was a nice experience, I felt very competitive but it was a big challenge that I took from zero, from no testing, not any similar race before it".
When asked about Le Mans, he answered: "We have not talked about this yet, but if there is an opportunity, I will try to use it".
Formula One F1 - Japanese Grand Prix 2017 - Suzuka Circuit, Japan - October 5, 2017.
He also raced for Minardi and Ferrari, from 2010-14, twice losing the world title to Sebastian Vettel, then of Red Bull, on the last day of the season. His last win was in Spain in 2013, again with the Italian team.
The Spanish driver, who won his two championship title in 2005 and 2006, believes that after facing three hard seasons with Honda's engine, the merger between McLaren and Renault could boost the team and would bring the competitiveness back.
"He's always been clear to me that this is a team he loves, and that his heart has always been set on staying".
The 36-year-old Spaniard has signed a new deal which is believed to be for one year with options to extend.
"The organisation now is much more logical in the way of winning in the short-term in Formula One".
Speaking to the media, Alonso said he'd be "extremely happy" to finish his career at McLaren.
"Obviously the last few years have been a big challenge and what you want is the best team and the best drivers in the world that you can get", he said.
"Our shareholders have ambitious plans for the whole group, and success within Formula 1 is a central pillar of that strategy. Fernando fully understands and buys in to the direction we are taking", he further added.