High above the cloistered, elegant city, the director turned a friend’s apartment into a moody and tropical oasis.

OVER THE PAST decade, the Italian filmmaker Luca Guadagnino, 54, has developed a vibrant, unexpected sideline: interior design. His films, including “Call Me By Your Name” (2017) and “Queer” (2024), are distinguished by their sumptuous, minutely observed scenic design, as well as by their ability to communicate visceral desire, so it would be logical to assume that his private interiors would follow those same impulses.

This is not the case, he insists. “When people compare my work as a cinema maker to my work designing interiors, that’s myopic,” Guadagnino says. “When dealing with cinema, I’m using imagery to create emotion. With interiors, I’m dealing with very real physical relationships.”

Primary among those relationships is the creative partnership with his longest-standing client, the e-commerce businessman Federico Marchetti, 56. It was Marchetti, the founder of the online fashion retailer Yoox (which later merged with Net-a-Porter), who in 2016 happened to read an interview with the director, an old friend, in which Guadagnino confessed his secret dream of being an interior designer. Marchetti offered up as a first commission the abandoned silk mill he’d recently purchased on Lake Como that he wanted transformed into a villa in which he would live with his wife, the British journalist Kerry Olsen, 49, and their daughter, Margherita, now a teenager. Since then, Studio Luca Guadagnino, the practice the director founded in 2017, has collaborated with Marchetti on a series of projects, including an overhaul of the entrepreneur’s original Milan bachelor apartment and an Art Deco-era residence for the family on Venice’s Lido. Over the years, decorating has become not merely a side hustle for Guadagnino but, like gardening, which he’s called his favorite avocation, a passion bordering on obsession. His studio now has a staff of 20.

On a mild midwinter afternoon, he was having lunch with Marchetti on one of the several densely planted terraces of the pair’s most recent creation: a 5,900-square-foot duplex penthouse atop a 10-story Daniel Libeskind residential tower in the CityLife complex that has risen in the past two decades on the site of Milan’s former fairgrounds. “Luca had, always, carte blanche, but in a collaborative way,” says Marchetti in a mild tone that a close friend once characterized as a “suede scabbard over steel.” Across the table, the director, who recently wrapped “Artificial,” loosely based on the life of the OpenAI co-founder Sam Altman, was inspecting a basket full of what looked like indistinguishable corn crackers before selecting one. The level of discernment was in character: Presented with three peas on a plate, he will have a favorite.

But working for flesh-and-blood clients means that Guadagnino must balance his idiosyncrasies with a psychoanalytical approach. “When you conceive of a space, you have to understand your clients very well,” he says. “To discover what it is they want — and also what they don’t know they want.”

With so many terraces, one thing that Marchetti and Olsen were sure they wanted this time around was “green, green, green — and very distant from historic Milan,” known for an insular elegance that careens from ultraminimalism to antiques-filled Baroque, says the director. Ideally, there’d be a hanging garden, even a jungle. The conversation “led to the Brazilian Modernists as examples of timeless classicism,” says Guadagnino, who instructs his team to research their design projects as he does his movies, compiling extensive historical dossiers instead of asking the client for mood boards or resorting to anything as quotidian as Pinterest. (“The orgy of images we are subject to creates a kind of bulimia. I work from the memory of things.”) The apartment’s pared-down sophistication, inside and out, was inspired by South American designers of the mid-20th century, including Lina Bo Bardi and Jorge Zalszupin, whose works often incorporated indigenous dark woods and flora. “We discussed how to pay homage to that idiom,” says Guadagnino, “specifically and literally, while moving forward from it. We thought a lot about this emphasis on sensual materiality and humane form.”

THOUGH TROPICAL PLANTS and vines — dracaena, monstera, areca palm — unify the angular spaces, threading themselves through doorways and overhangs, the relatively formal layout of the H-shaped apartment was dictated by the three inhabitants’ desire for their own spaces. Each has a private domain, sparsely decorated, punctuated by such important pieces as Franco Albini’s 1938 rocking chaise longue in Olsen’s studio and a version of Ludwig Mies van der Rohe’s 1927 MR chair pulled up to Margherita’s desk. The public rooms — the ones in which the family meets — are less austere. Marchetti, the son of a Fiat factory manager father and a mother who worked as a telephone operator, has always insisted on a distinct separation of public and private spaces: Until he was 13, he shared a bedroom with his parents in a small apartment in the Byzantine town of Ravenna.

On the main floor, down a 65-foot-long hallway from the primary suite, with its simple bed draped with a persimmon silk textile from India, is the living room, where the Afro-Brazilian influence on Modernism and Guadagnino’s comfort with juxtapositions are in full bloom. José Zanine Caldas’s 1965 Namoradeira chair — a curved pequi wood version of a Victorian tête-à-tête — is placed by Sergio Rodrigues’s chastely linear 1963 Paraty seat, originally made for the Itamaraty Palace in Brasília, Lucio Costa and Oscar Niemeyer’s famed planned city.

The art is hung with a similar disregard for convention: On a wall in the living room is a huge mirrored stainless steel Anish Kapoor disc; on the floor above it, a Picasso still life hangs in the library. The wavelike curved plaster staircase that connects the two rooms features rattan cladding and a contrasting white lacquered wood railing — an example of Guadagnino’s preoccupation with texture. Such tactile surfaces are, he says, “one of the great pleasures of design, as important as the more formal elements.”

The director’s infatuation with color and light, evident in all his films, is seen here in the dining room and kitchen, which are at the center of the apartment. In the dining room, where the family gathers for meals — fresh produce often comes from their garden on Lake Como — a rare brass circa 1950 Snowflake fixture by the Finnish lighting pioneer Paavo Tynell hangs above an oval-shaped ash wood table by the Milanese architect Umberto Riva, paired with a set of Gio Ponti’s classic Superleggera chairs, designed in 1957. The dining room walls are covered with custom-made tiles in supersaturated shades of fire engine red, poison green and mauve, hand-painted, hand-glazed and arrayed in an abstract pattern in collaboration with the Irish architect Nigel Peake. Unsurprisingly, perhaps, considering Guadagnino’s reputation for precision, his team demanded that the tiles, which butt up against a sober metal panel inlaid with a grid of portholes — a detail repeated in many of his interiors — be repeatedly remade until they were satisfied with their intensity. The kitchen, with polished steel cabinetry and counters that seem cut from a single sheet of metal, has walls tiled with hibiscus pink zellige and a poured-concrete floor tinted the blue of vintage sugar boxes.

From the terrace beyond, Guadagnino and Marchetti might well be two longtime friends relaxing atop a São Paulo high-rise. But with the views of the ancient Italian city below, its green spaces largely crowded out by low-lit palazzos behind heavy doors, the sun-dappled space seems unmoored in time and place. “Yes, it is eccentric,” says the director, “but to me, that is very Milanese.”