Nan Rosenthal, a museum curator who was a champion of contemporary art at the National Gallery of Art and the Metropolitan Museum of Art, two museums better known for their collections of Old Masters and French Impressionists, died April 27 at her home in Manhattan. She was 76.

She had a heart attack, said a sister-in-law, Wendy Mackenzie.

Ms. Rosenthal, who began her career as a journalist, came to the National Gallery in 1985 as a curator of 20th-century art under museum director J. Carter Brown. She used her extensive connections in the art world to acquire important works for exhibitions, sometimes approaching the artists directly.

Working alongside another curator, Jack Cowart, she was instrumental in helping the National Gallery acquire major works by Barnett Newman, Robert Rauschenberg and other artists.

In 1987, Ms. Rosenthal described to The Washington Post how she managed to arrange a long-term loan of Andy Warhol’s paintings of Campbell’s soup cans for the National Gallery.

Nan Rosenthal, a former curator at the National Gallery of Art in Washington and the Metropolitan Museum of Art in New York. (Metropolitan Museum of Art)

“This is how it happened,” she said. “I was at a party at Robert Rauschenberg’s New York studio, a party called to show Bob’s new work to his friends. [Art dealer] Irving Blum was there. I said, ‘Irving, what are you doing with Andy’s soup cans?’ He said, ‘Do you want to borrow them?’ I said, ‘Yes,’ and he said, ‘Fine.’ I couldn’t believe it. I said, ‘Deal?’ He said, ‘Deal.’ It was the fastest show I ever arranged for the National Gallery of Art.”

Ms. Rosenthal helped curate several exhibitons at the National Gallery, including 1989’s “Box in a Valise,” a series of miniature constructions by the French absurdist Marcel Duchamp. Washington Post art critic Paul Richard described the display, which continued miniatures, replicas and photographs, as “part treasury, part toy box, part one-man retrospective,” which “hilariously, ironically, subverts the whole idea of a permanent museum of masterworks of art.”

At the National Gallery, Ms. Rosenthal was perhaps best known for curating a 1990 retrospective of the drawings of Jasper Johns. The exhibition was designed by Johns himself.

In 1993, Ms. Rosenthal moved to the Metropolitan Museum in New York, where she curated exhibitions of Willem de Kooning’s paintings (1994), Jackson Pollock’s drawings (1997-98), prints by Chuck Close (2004) and mixed-media works by Rauschenberg (2005-06).

In her final exhibition before her retirement from the Metropolitan Museum in 2008, Ms. Rosenthal returned to the work of Johns, examining the artist’s use of the color gray. In a 2008 PBS interview with Charlie Rose, Ms. Rosenthal described Johns as the country’s greatest living artist.

His genius was in “his touch,” she said, in “the strokes that he makes on the surface of the canvas.”

Nan Rosenthal was born Aug. 27, 1937, in New York. After graduating from Sarah Lawrence College in Bronxville, N.Y., she worked at the New York Post and in Europe for the International Herald Tribune and London Evening Standard.

She was an editor at Art in America in the 1960s and received master’s and doctoral degrees in art history from Harvard University in 1970 and 1976, respectively. She taught at the University of California at Santa Cruz, at Princeton University and other colleges before becoming a museum curator.

Her first marriage, to artist Otto Piene, ended in divorce.

Survivors include her husband of 23 years, Henry B. Cortesi of New York.