The 37-year-old Spaniard teams up again with Sebastien Buemi and Kazuki Nakajima with whom he triumphed 12 months ago.
Alonso is back at the classic race behind the wheel of a Toyota although he will start the race on Saturday from second on the grid after the Japanese manufacturer's other car of Mike Conway, Kamui Kobayashi and Jose Maria Lopez claimed pole position.
"I feel good with the result (of qualifying); it's job done for us," said Alonso who is contesting Le Mans having failed in his latest bid to complete motor racing's 'Triple Crown' when he missed out on qualifying for the Indy 500 last month.
"We wanted to get both Toyotas on the front row and we managed it. The privateers were very close but we performed well to stay ahead and also get ready for the weekend.
"It's always tough to race for 24 hours so we will prepare ourselves well on Friday and be ready for the fight," added Alonso who is still in contention for the overall world endurance championship title this season.
Despite his caution, a win for the Toyota hybrids is almost certain - barring an accident.
For the last two seasons, they have been the only manufacturer on the grid after Porsche and Audi pulled out of the elite LMP1 class which this year features just six other cars.
Kobayashi, who once drove for Toyota when the company fielded a team in F1, said he had hoped to mark pole position with a new lap record.
"I am happy to be on pole again here. Actually I was hoping I could improve on my 2017 lap record but I was missing a little bit of time," said the 32-year-old.
"Two years ago the track conditions and traffic were perfect; it wasn't quite the same this time. But it's a great feeling to be on pole and now we put all our effort to get the result on Sunday afternoon."
He then added ruefully: "It's my second pole position but I would like to win at least once."
Although Alonso will not be back in 2020, Toyota will be on the grid after confirming they will enter a 'hypercar' under new regulations aimed at boosting competition and trimming costs.
Aston Martin said they too will send a team next year.
"The hypercar lap times should be similar to the Toyota TS050 Hybrid," said Pascal Vasselon, the technical director of the Toyota racing team.
"First, because in the new regulations the onus is on cost-effectiveness rather than a quest for performance and second, because the aerodynamics will be less efficient. Our goal is simple: to make Toyota part of the legend of Le Mans."
The race gets underway on Saturday at 1300 GMT.