The youngest child of Gwen Hagen (an artist and advertising executive) and Earl Hagen (an attorney), Daron Aric Hagen (born 1961, Milwaukee, Wisconsin) was given the name of an older brother who — born with birth defects — died in infancy. His parents raised their children in a Frank Lloyd Wright-style cedar house on a large wooded lot in what was then countryside in New Berlin, west of Milwaukee.

Hagen began piano lessons at the age of seven and began composing at the age of eleven. Lessons in piano, conducting, orchestration and theory at the Wisconsin Conservatory of Music prepared him for his debut at fifteen, when he conducted the premiere of his first orchestral piece with a Milwaukee youth orchestra. His mother sent a score and recording of the piece to Leonard Bernstein, who enthusiastically urged Hagen to attend Juilliard to study with David Diamond. After two years at the University of Wisconsin, Madison, followed by three years of study with Ned Rorem at the Curtis Institute of Music in Philadelphia, Hagen moved to New York City in 1984 to complete his formal education as a student of Diamond's at Juilliard. After graduating, Hagen lived in Europe briefly, first at the Camargo Foundation in Cassis, France, and then at the Rockefeller Foundation's Villa Serbelloni in Bellagio, Italy. When he returned to the United States, Hagen studied privately with Bernstein, whose guidance during the composition of Hagen's Shining Brow (1992) — the opera that launched Hagen's career internationally — prompted him to dedicate the score to Bernstein's memory.

Hagen's music drew attention as early as 1981, when at the age of twenty, his Prayer for Peace was premiered by the Philadelphia Orchestra — the first Curtis-student work that the orchestra had premiered since its introduction fifty years earlier of music by another Curtis student, Samuel Barber. Five years later he made his concerto debut as piano soloist with the Denver Chamber Orchestra. Hagen's numerous commissions from major orchestras and performers between 1981 and 2005 include a dozen major orchestral works, three symphonies, seven concertos (for Gary Graffman, Jeff Khaner and Sara Sant'Ambrogio, among others), several massive works for chorus and orchestra, two dozen choral works, ballet scores, concert overtures, showpieces, two brass quintets, two piano trios, a string quartet, an oboe quintet, a duo for violin and cello, solo works for piano, organ, violin, viola, and cello, and seventeen published cycles of art songs on poetry of over fifty poets.

Hagen has composed seven operas: Shining Brow (1992), The Elephant's Child (1994), Vera of Las Vegas (1996), Songs of Madness and Sorrow (1996), Bandanna (1998), Broken Pieces (2003), and The Antient Concert (2005). He is currently working on Just for the Night (his second opera on a libretto by Barbara Grecki), The Smithsonian Institution, and Amelia (for the Seattle Opera).

Hagen's music has been awarded a 2005 National Endowment for the Arts production grant, two Rockefeller Foundation Residencies at Bellagio in Italy, the Camargo Foundation residency in France, the Columbia University Bearns Prize, the Charles Ives Fellowship from the American Academy of Arts and Letters, a Barlow Foundation grant and prize, multiple prizes from the BMI and ASCAP Foundations including the ASCAP-Nissim Prize for Orchestral Music, Opera America's 'Next Stage' Award, a production grant from the Readers Digest Opera for a New America Project, and the Kennedy Center Friedheim Prize for orchestral music.

In 2004 Hagen was named President of the Lotte Lehmann Foundation in New York City, an international nonprofit organization dedicated to encouraging the performance and creation of art song. A passionate educator, ambassador of the arts, and advocate of young composers, he has served twice as Composer in Residence for the Princeton University Atelier (1998, 2005); as Artist in Residence at the University of Nevada, Las Vegas (2000-2002); Sigma-Chi-William P. Huffman Composer in Residence at Miami University, Oxford, Ohio (1999-2000); Artist in Residence at Baylor University, Waco, Texas (1998-1999); on the musical studies faculty of the Curtis Institute of Music (1996-1998); as an Associate Professor at Bard College (1988-1997); as a Visiting Professor at the City College of New York (1997, 1993-1994); and as a Lecturer in Music at New York University (1988-1990). In the late 1980's, he became a Member of the Corporation of Yaddo, where he has composed many of his works.

Hagen has lived in New York City since 1984. Recordings of his music appear on Arsis,. Albany, Arabesque, CRI, Sierra, Klavier, and other labels. Carl Fischer in New York City publishes Hagen’s music; prior to 1990 E.C. Schirmer in Boston published his works. Schott represents his catalogue in Europe.