He grew up in Dubuque, Iowa. He graduated from Loras College and the University of Chicago. He married Loretta D'Agostino in 1960; they have five children togetehr. He taught at Illinois Institute of Technology, University of Wisconsin–Milwaukee and California State University, Sacramento. His students include Raymond Carver, Charlene Ungstad and Gary Short, and Gary Thompson.
He lives in Sacramento.
- poet laureate of Sacramento, California
- 1978 Guggenheim Fellow 
- 1976-1977, 1985–1986, 1992-1993 Fellow National Endowment for the Arts
- 1987-1988 Shelley Memorial Award
- Animism (Oberlin College Press, 2014)
- The Truth Squad (Copper Canyon Press, 2002)
- About Night: Selected and New Poems (Oberlin College Press, 1993)
- Eden (University of Illinois Press, 1989)
- Singing (Ecco Press, 1985)
- String (Ecco Press, 1980)
- Goodwill, Inc (1976)
- Double Exposures (1971)
- We Weep for Our Strangeness (1969)
- Dennis Schmitz (ed.). The Sacramento Anthology of 100 Poems. Sacramento’s Poet Laureate Program; Sacramento Metropolitan Arts Commission.
Schmitz is the kind of poet whose work is unknown to the general public but eagerly read by other writers in top literary magazines like Field or Antaeus. In this volume, he continues the exciting work he has already done with dramatic monologues and religious meditations set on California farms or in the construction sites, flophouses, and movie palaces of Chicago.
- SANDYE VOIGHT (September 18, 2003). "Poet making trek back to his Dubuque roots; Schmitz will give a reading tonight at the Carnegie-Stout Library". Dubuque Telegraph - Herald.
- Europa Publications, ed. (2003). International Who's Who in Poetry 2004. Taylor & Francis. ISBN 978-1-85743-178-0.
- Carver, Raymond; Gentry, Marshall Bruce; Stull, William L (January 1990). Conversations with Raymond Carver. ISBN 978-0-87805-449-7.
- Sklenicka, Carol. Raymond Carver: A Writer's Life. New York: Scribner, 2009
- "Notes on Current Books, Autumn 1980". Virginia Quarterly Review. Autumn 1980.