Harold Bauer was born in Kingston upon Thames; his father was a German violinist and his mother was English. He took up the study of the violin under the direction of his father and Adolf Pollitzer. He made his debut as a violinist in London in 1883, and for nine years toured England. In 1892, however, he went to Paris and studied the piano under Ignacy Jan Paderewski for a year, though still maintaining his interest in the violin. An anecdote reports that Paderewski jokingly told Bauer to concentrate on the piano because "You have such beautiful hair". In 1893, in Paris, he and Achille Rivarde premiered Frederick Delius's Violin Sonata in B minor.
During 1893-94 he travelled all through Russia accompanying the noted soprano Mademoiselle Nikita and giving piano recitals and concerts, after which he returned to Paris. Further recitals in the French capital brought him renown, and he almost immediately received engagements in France, Germany and Spain. His reputation was rapidly enhanced by these performances, and his field of operation extended through the Netherlands, Belgium, Switzerland, England, Scandinavia and the United States.
In 1900, Harold Bauer made his debut in America with the Boston Symphony Orchestra, performing the U.S. premiere of Johannes Brahms' Piano Concerto No.1 in D minor. On 18 December 1908, he gave the world premiere performance of Claude Debussy's piano suite Children's Corner in Paris. After that he settled in the United States, and was a founder of the Beethoven Association.
Harold Bauer was also an influential teacher and editor, heading the Piano Department at the well known Manhattan School of Music. Starting in 1941, Bauer taught winter master classes at the University of Miami and served as a Visiting Professor at the University of Hartford Hartt School of Music with Maestro and Founder - Moshe Paranov and head of the Piano Department - Raymond Hanson, from 1946 until his death in 1951. 
He published Harold Bauer, His Book (New York, 1948).
Bauer was married twice. He had been married to Marie Knapp (1873–1940) until her death. Sometime between 1940 and 1943, Bauer married again, to concert pianist, colleague, and former student Wynne Pyle. He had no children by either marriage.
- A Review of the Complete Acoustic Solo Recordings of Harold Bauer
- Harold Bauer plays Bach - Chromatic Fantasy and Fugue in Dm - Phillips/Duo-Art Rolls 7316/7317, issued Apr-1929
- The Art of the Piano. Its performers, literature, and recordings. Third edition, by David Dubal. The Pianists section begins on page 11. Pompton Plains, NJ: Amadeus Press, 2004.
- The ASCAP Biographical Dictionary. Third edition, New York: American Society of Composers, Authors and Publishers, 1966
- Baker's Biographical Dictionary of Musicians
- Sixth edition, revised by Nicolas Slonimsky, London: Collier Macmillan Publishers
- Seventh edition, revised by Nicolas Slonimsky, New York: Macmillan Publishing Co., Schirmer Books, 1984
- Eighth edition, revised by Nicolas Slonimsky, New York: Macmillan Publishing Co., 1992
- Ninth edition, edited by Laura Kuhn, New York: Schirmer Books, 2001
- Baker's Biographical Dictionary of Twentieth-Century Classical Musicians, by Nicolas Slonimsky, New York: Schirmer Books, 1997
- Biographical Dictionary of American Music. By Charles Eugene Claghorn (1911–2005), West Nyack, New York: Parker Publishing Co., 1973
- Biography Index; A Cumulative Index to Biographical Material in Books and Magazines, New York: H.W. Wilson Company
- Volume 1: January 1946–July 1949 (1949)
- Volume 2: August 1949–August 1952 (1953)
- Volume 3: September 1952–August 1955 (1956)
- Volume 4: September 1955–August 1958 (1960)
- Volume 7: September 1964–August 1967 (1968)
- Volume 8: September 1967–August 1970 (1971)
- Volume 9: September 1970–August 1973 (1974)
- Volume 11: September 1976–August 1979 (1980)
- Volume 12: September 1979–August 1982 (1983)
- Volume 16: September 1988–August 1990 (1990)
- Volume 21: September 1995–August 1996 (1996)
- Britannica Book of Music, edited by Benjamin Hadley, Garden City, New York: Doubleday & Co., 1980
- The Cambridge Dictionary of American Biography, edited by John S. Bowman, Cambridge, England: Cambridge University Press, 1995
- Musicians since 1900; Performers in Concert and Opera, compiled and edited by David Ewen, New York: H.W. Wilson Company, 1978
- The New American Dictionary of Music, by Philip D. Morehead with Anne MacNeil, New York: Dutton, 1991
- The New Grove Dictionary of American Music, four volumes, edited by H. Wiley Hitchcock & Stanley Sadie, London: Macmillan Press, 1986
- The New Grove Dictionary of Music and Musicians, 20 volumes, edited by Stanley Sadie, London: Macmillan Publishers, 1980
- Notable Twentieth-Century Pianists: A Bio-Critical Sourcebook, two volumes, by John Gillespie & Anna Gillespie, Westport, Connecticut: Greenwood Press, 1995
- The Penguin Companion to Classical Music, by Paul Griffiths, London: Penguin Books, 2004
- The Penguin Dictionary of Musical Performers: A Biographical Guide to Significant Interpreters of Classical Music — Singers, Solo Instrumentalists, Conductors, Orchestras and String Quartets — Ranging From the Seventeenth Century to the Present Day, by Arthur Jacobs, London: Viking Press, 1990
- The Pianist's Dictionary, by Maurice Hinson, Bloomington, Indiana: Indiana University Press, 2004
- American National Biography, 24 volumes, edited by John A. Garraty & Mark C. Carnes, New York: Oxford University Press, 1999
- Dictionary of American Biography, Supplement 5, New York: Charles Scribner's Sons, 1977
- Who Was Who in America, A Component of Who's Who in American History, Vol. 3, 1951–1960, Chicago: Marquis Who's Who, 1966
- Free scores by Harold Bauer at the International Music Score Library Project (IMSLP)
- Harold Bauer at Find a Grave