He joins from a role as head chef at W Leicester Square, and has previously cooked at Rosewood London, Sushisamba and Nobu London.
Castaldo's CV also includes time at Lasarte in Barcelona, which now holds three Michelin stars.
In his new role the chef will oversee the five-star hotel's room service, events and private dining catering, and the Library Bar.
The Lanesborough says his passion for culinary creativity and professionalism make him a ‘perfect addition’ to the food team.
The Hyde Park Corner hotel is also home to Michelin-starred Celeste, which is overseen by French chef Eric Frechon – who won three stars at Le Bristol in Paris – and his protégé Florian Favario.