Former champions McLaren announced the Frenchman's departure on Tuesday in a statement detailing organisational changes within the team.
Sanchez had joined from Ferrari, after spending nearly a year on 'gardening leave', in January as technical director for car concept and performance but McLaren said the position was being streamlined to focus on performance.
Team principal Andrea Stella will assume the role until a permanent replacement is found while Rob Marshall, who joined from Red Bull at the same time as Sanchez, becomes chief designer.
Neil Houldey takes on the role of technical director for engineering.
"Following thoughtful discussions between David Sanchez and the team leadership, the mutual decision has been taken for David to leave the team," said Stella of the surprise move.
"Upon our joint reflection, it became apparent that the role, responsibilities and ambitions associated with David's position did not align with our original expectations when he agreed to join us in February 2023."
McLaren, with Lando Norris (24) and Oscar Piastri (22), are third in the constructors' standings ahead of this weekend's Japanese Grand Prix at Suzuka.
