Hirakawa will become part of McLaren's driver development programme, supporting the Woking team in its simulator as well as conducting a testing programme with its 2021 MCL35M car.
The 29-year-old will dovetail his F1 testing role with his current drive for Toyota, with which he is currently leading the Hypercar class in the World Endurance Championship.
Hirakawa and his team-mates Sebastien Buemi and Brendon Hartley are the reigning champions too, having won both the overall title and the Le Mans 24 Hours in 2022.
“I’m happy to have joined the McLaren F1 team as a reserve driver," Hirakawa said in the margin of this weekend's Japanese Grand Prix.
"It’s an exciting prospect to work with such a respected team and I’m grateful to Zak [Brown] and Andrea [Stella] for the opportunity.
"I’ve already met the team and experienced the simulator at MTC which has allowed me to hit the ground running. I’m now fully prepared and focused for the remainder of 2023.
"I am grateful to [Toyota Gazoo Racing] for allowing me to serve as a driver for the two teams. The second thank you goes to Morizo-san [Toyota chairman Akio Toyoda], who has supported me as a driver."
Source: Autosport