Slonczewski was born at Hyde Park, New York and raised in Katonah, New York.

She earned an A.B. in biology, magna cum laude, from Bryn Mawr College in 1977. She completed a Ph.D. in Molecular Biophysics and Biochemistry from Yale University in 1982 and post-doctoral work at the University of Pennsylvania studying calcium flux in leukocyte chemotaxis. Since 1984 she has taught at Kenyon College, taking sabbatical leaves at Princeton University and the University of Maryland, Baltimore. Slonczewski's research focuses on the pH (environmental) stress response in Escherichia coli and Bacillus subtilis using genetic techniques.

Slonczewski teaches both biology and science fiction courses. From 1996 through 2008, she has been awarded Howard Hughes Medical Institute funding for undergraduate biological sciences education, which she uses to improve science instruction and to foster summer science fellowships for minority and first-generation students.

Slonczewski is also a member of the Quakers and Quakerism is featured in many of her novels.

Her 1986 Campbell Award-winning novel A Door Into Ocean shows her command of genetics and ecological science, as well as her commitment to pacifism and feminism. It depicts the ecosystem of a planet covered entirely by water, inhabited by an exclusively female race of genetic engineers. Daughters of Elysium (1993), The Children Star (1998), and Brain Plague (2000) are loose sequels.

A serialization of her The Children Star (1998) appeared in Analog Science Fiction and Fact, a magazine known for hard science fiction.

Her most recent book, Brain Plague (2000) depicts a world where intelligent microbes inhabit human brains. The microbial aliens have potential for great good as well as great evil. They evolve in the same way as pathogens such as the AIDS virus or as symbionts such as our digestive bacteria, which help keep humans healthy. Brain Plague tells of a future in which genetic engineering, combined with nanotechnology can do everything from shaping our bodies to growing enormous buildings for us.

Novels

• Still Forms on Foxfield (1980) 1988 reprint ISBN 0380753286
• A Door Into Ocean (1986) ISBN 0877957630
• The Wall Around Eden (1989) ISBN 1557100306
• Daughter of Elysium (1993) ISBN 0380972220
• The Children Star (1998) ISBN 0312867166
• Brain Plague (2000) ISBN 0312867182