Her early work is associated with the Boston Expressionist school; later she became known for her still-life paintings in which light is refracted through glass and water, and for her portraits.

Her paintings from this period are loosely associated with the Boston Expressionist school, although her themes tended to be gentler than those of Jack Levine and others working in that style.

In a 1957 review of her show at the Boris Mirski Gallery, critic Edgar Driscoll marveled at her ability to render tranquil domestic scenes, featuring sleeping children or nursing infants, in a creative way: "It is a tender, touching showing...Yet the artist, through strong color and off-beat compositions, carefully avoids over-sentimentalizing or slipping into the banal.

Swan provided pen and ink illustrations for several of Sexton's books, including Transformations, The Death Notebooks, and Live or Die, the last of which won the Pulitzer Prize for Poetry.

[9] Critic Vernon Young, reviewing Transformations in 1972, wrote, "The drawings of Barbara Swan incisively complement the poems.

John N. Morris, reviewing Up Country in 1974, called them "prettifications" and complained that "they draw too much attention to the slightly ladylike quality of a few of these poems, the air they have of essays in the female georgic.

"[11] Swan drew and painted portraits of Sexton, concert pianist Luise Vosgerchian,[6] writer Tillie Olsen, historian James F. O'Gorman, composer Arthur Berger, and artists Sigmund Abeles, Gregory Gillespie, Harold Tovish, and Esther Geller, among others.