Located in Liverpool's city centre, Fettle's refurbishment was designed to reinvigorate the restaurant and offer a "spectacularly opulent and contemporary take on traditional Italian dining", the studio said.
During the redevelopment, Fettle stripped the building back to its existing shell and redesigned each element, from the walls to the flooring.
The 280-square-metre restaurant also contains a feature bar and a private dining room named The Rosa Room and Wine Sellar, which is located on the lower ground floor.
San Carlo's colour palette takes cues from the hues of the northern Italian coastline and includes greens, blues and pinks.
The furniture was designed specifically for the project and was informed by the furniture found in grand Milanese villas and gardens.
This included fluted oak bar stools with green leather seats and brass bases, marble and timber tables, curved-legged dining chairs and velvet leather seating.
"The restaurant offers a spectacularly opulent and contemporary take on traditional Italian dining with elegant interiors inspired by Grand Milanese villas and gardens," the studio said.
The lighting was chosen to add a sense of softness to the interior, and includes a mixture of bespoke-designed statement chandeliers, pendant fillings and wall and table lamps to give the space an "intimate glow".
The floor was equipped with colourful terrazzo in a mix of cream, orange and green tones, while the walls were clad in high gloss timber panelling.
According to the architects, its colour is similar to that of luxury Italian sports cars and the water taxis of Venice.
The restaurant was also equipped with antiqued mirrored panels that aim to add to the glamour of the space.
Three eclectic abstract murals by Los Angeles-based artist Jessalyn Brooks are positioned opposite the bar and on the rear wall of the restaurant.
"We're excited to unveil the transformation of San Carlo Liverpool," said the managing director of San Carlo, Marcello Distefano. "The new design is representative of the evolution of San Carlo, a journey we began in 1992."
Fettle was founded by designers Tom Parker and Andy Goodwin and specialises in hospitality design and interior architecture.
Previous projects include the restoration of an art deco hotel in Santa Monica, California, and the conversion of a members' club for 1 Warwick members' club in Soho, London.
Other interior projects recently featured on Dezeen include the transformation of a three-story home into a restaurant in Bogotá that uses natural materials and a travelling gallery by multidisciplinary designer Vanessa Heepen, which includes vintage furniture pieces.