Born in Cobourg, Ontario, Canada, she moved with her family to New York at a young age. When she was fourteen, she moved to Maryland where she lived for the rest of her life. Jacobsen served as poetry consultant to the Library of Congress from 1971 to 1973 and as honorary consultant in American letters from 1973 to 1979. She served as member of both the literature panel for the National Endowment of the Arts and of the poetry committee of Folger Library.
She was a prolific writer of poems and short-stories into her ninth decade. Joseph Brodsky praised her poetry for its "reserve, stoic timbre, and its high precision" while William Meredith called her "post-cocious" for her prolific writing late in life.
Jacobsen is the author of several collections of poetry and prose. Among her awards are an Academy of American Poets fellowship and the 1997 Poets' Prize (for In the Crevice of Time). She received honorary doctorates from Goucher College, The College of Notre Dame in Maryland, Towson State University, and Johns Hopkins University. She was inducted into The American Academy of Arts and Letters in 1994 and received the Robert Frost Medal for Lifetime Achievement in Poetry.
Jacobsen was also a fan of the Baltimore Orioles baseball team and wrote poems on her love of baseball.