Berlage spent fifteen years on this project and died in 1934, a year before its opening. His son-in-law, Emil Emanuel Strasser, oversaw the final touches. The first reviewers were split. The outside was deemed plain, even disappointing, a long low building of yellow brick on the green edge of The Hague. Then they walked through the doors. The entrance hall, with its coloured tiles and slender columns, drew immediate praise. One newspaper conceded that the exterior offered little to admire, but the interior was "pleasant, calming and intimate." Another journalist, struck by the daylight pouring through Berlage's adjustable skylights, simply wrote: "Light, light, Berlage has captured the magic of light here." The bricks themselves are a deception. The structural building underneath is iron and reinforced concrete; the bricks were laid afterward as pure decoration, each course set perpendicular to the one below it, weaker than ordinary masonry but visually richer.

The museum's origin is older than its building. On 29 May 1866, a group of artists and collectors gathered in The Hague to found the Society for the Development of a Museum of Modern Art. The painter Hendrik Willem Mesdag joined later. Princes Frederik and Alexander of the Netherlands signed on as members. By 1871 the city council had agreed to host their growing collection in a council museum on the Korte Beestenmarkt, and within months Queen Wilhelmina was visiting. The Society outgrew that space, moved to the St Sebastian building in 1884, and outgrew that too. Director Hendrik van Gelder, appointed in 1912, decided the museum needed a building made for it, not borrowed from someone else. He approached Berlage in 1919. War, council debates, and Berlage's own perfectionism stretched the project across the next sixteen years.

Piet Mondrian spent his youth in Winterswijk, in the far east of the Netherlands, but his afterlife belongs to The Hague. In 1951 the collector Sal Slijper began donating Mondrian paintings to the museum. In 1971 his estate left it the rest: 190 Mondrians plus 12 works by his contemporaries. The museum can now trace the artist's whole arc, from the early naturalist landscapes to the strict red-blue-yellow grids that became the visual signature of the twentieth century. Mondrian was working on Victory Boogie-Woogie in New York in 1944 when he died. The canvas, still bearing the coloured tape he used to test compositions, hangs here. In 1966 the Gemeentemuseum staged a moment of pure pop fusion: Yves Saint Laurent's Mondrian-inspired dresses, those cocktail shifts of bold colour blocks, presented in the rooms full of the paintings that inspired them.

Around 165,000 objects fill the building and its sister institutions. The modern art galleries hang Degas, Monet, Picasso, Schiele, Van Gogh, Jongkind, Charley Toorop and Jan Toorop on the same walls. The print room holds roughly 50,000 drawings and posters by everyone from Ingres to Toulouse-Lautrec, Klee to Odilon Redon. Down another corridor sits one of the largest Dutch Delftware collections anywhere, blue-and-white plates and tulip vases catching the daylight Berlage engineered. Persian ceramics and glass occupy still other rooms. The Kunstmuseum also runs KM21, a contemporary art space across the courtyard, and Fotomuseum Den Haag, devoted to photography. The Berlage building shelters around 25 to 30 exhibitions a year. The 2021 exhibition Monet: The Garden Paintings was voted the best museum show in the Netherlands.

When the Germans invaded on 10 May 1940 the museum staff moved fast. Boy Scouts helped carry paintings, removed from their frames, into the museum's underground depot. The country surrendered within days; the works went back on the walls before the end of May. The reprieve was brief. In 1942 the occupiers marked the museum for demolition to build a defensive line through The Hague. Heavy protests from staff redirected the plan, but the collection was no longer safe in the basement. In fourteen frantic days every artwork was hauled out and hidden in bunkers around the Netherlands. The Germans turned the empty galleries into storage. Director Gerhardus Knuttel was reported to have resigned honourably in 1943; in fact he had been sent to a prisoner of war camp for refusing to cooperate. The collection returned. The building survived. Berlage's elevens still measure the rooms.