Millon was born in 1928, the only child of immigrant Jewish parents from Lithuania and Poland. His 19th-century ancestors came from the town of Valozhyn, then a part of the Russian Empire.:309 Receiving degrees from both American and European universities, he was a member of the board of trustees of Allentown State Hospital, a large Pennsylvania psychiatric hospital for 15 years. Shortly thereafter he became the founding editor of the Journal of Personality Disorders and the inaugural president of the International Society for the Study of Personality Disorders. He is Professor Emeritus at Harvard Medical School and the University of Miami.
The American Psychological Foundation presents an award named after Millon, known as the "Theodore Millon Award in Personality Psychology," to honor outstanding psychologists engaged in "advancing the science of personality psychology including the areas of personology, personality theory, personality disorders, and personality measurement."
Millon has written numerous popular works on personality, developed diagnostic questionnaire tools such as the Millon Clinical Multiaxial Inventory, and contributed to the development of earlier versions of the Diagnostic and Statistical Manual of Mental Disorders.
Among other diagnoses, Millon advocated for an expanded version of passive aggressive personality disorder, which he termed 'negativistic' personality disorder and argued could be diagnosed by criteria such as "expresses envy and resentment toward those apparently more fortunate" and "claims to be luckless, ill-starred, and jinxed in life; personal content is more a matter of whining and grumbling than of feeling forlorn and despairing" (APA, 1991, R17). Passive-Aggressive Personality Disorder was expanded somewhat as an official diagnosis in the DSM-III-R but then relegated to the appendix of DSM-IV, tentatively renamed 'Passive-Aggressive (Negativistic) Personality Disorder'.
Millon's personality disorder subtypes
- Sadistic (psychopathic) personality disorder subtypes 
- Self-defeating (masochistic) personality disorder subtypes
- Schizotypal personality disorder subtypes
- Schizoid personality disorder subtypes
- Paranoid personality disorder subtypes
- Antisocial (sociopathic) personality disorder subtypes
- Borderline personality disorder subtypes
- Histrionic personality disorder subtypes
- Narcissistic personality disorder subtypes
- Dependent personality disorder subtypes
- Obsessive-compulsive personality disorder subtypes
- Avoidant personality disorder subtypes
- Passive-aggressive (negativistic) personality disorder subtypes
- Depressive personality disorder subtypes
- Exuberant/Hypomanic (turbulent) personality disorder subtypes
- Decompensated Personality Disorder 
- Millon, Theodore (with Roger D. Davis) (1996) Disorders of Personality: DSM IV and Beyond 2nd ed. New York: John Wiley and Sons. ISBN 0-471-01186-X
- Millon, Theodore (2000). Personality Disorders in Modern Life. New York: John Wiley and Sons. ISBN 0-471-23734-5
- Millon, Theodore. (2004) Masters of the Mind. Hoboken: John Wiley and Sons.
- Millon, Theodore and Grossman, Seth.(2007) Moderating Severe Personality Disorders: A Personalized Psychotherapy Approach. Hoboken: John Wiley and Sons.
- Millon, Theodore and Grossman, Seth.(2007) Resolving Difficult Clinical Syndromes: A Personalized Psychotherapy Approach. Hoboken: John Wiley and Sons.
- Millon, Theodore and Grossman, Seth.(2007) Overcoming Resistant Personality Disorders: A Personalized Psychotherapy Approach. Hoboken: John Wiley and Sons.
- Blaney, Paul H. and Millon, Theodore (Eds). (2008) Oxford Textbook of Psychopathology, 2nd Ed.. New York: Oxford University Press.
- Millon, Theodore, Krueger, Robert and Simonsen, Erik (Eds). (2008). Contemporary Directions in Psychopathology: Toward the DSM-V and ICD-11. New York: Guilford Press.
- The Millon inventories: a practitioner's guide to personalized clinical assessment. (2008) Guilford Press. ISBN 978-1-59385-674-8
- Millon Clinical Multiaxial Inventory
- Pyotr Gannushkin (1875-1933), a Russian psychiatrist that created classification system for personality disorders, known by then as "psychopathies"
- "Test Developer Profiles — Theodore Millon, Ph.D., D.Sc.". McGraw-Hill. 2001. Retrieved January 22, 2010.
- Kinder, Bill N.; Strack, Stephen (2006). Pioneers of personality science: autobiographical perspectives. New York: Springer Pub. Co. ISBN 0-8261-3205-7.
- "Biography of Dr. Theodore Millon". The Institute for Advanced Studies in Personology and Psychopathology. 2006. Retrieved January 22, 2010.
- Browning, Julie (October 29, 2005). "Theodore Millon – Grandfather of Personality Theory". All in the Mind. Australian Broadcasting Corporation. Retrieved January 22, 2010.
- No Authorship Indicated. "Gold Medal Award for Life Achievement in the Application of Psychology". The American Psychologist 63 (5): 345–7. doi:10.1037/0003-066X.63.5.345. ISSN 0003-066X. Retrieved January 22, 2010.
- "Theodore Millon Award in Personality Psychology". American Psychological Association. 2010. Retrieved January 22, 2010.
- Lane, C. (1 February 2009). "The Surprising History of Passive-Aggressive Personality Disorder". Theory & Psychology 19 (1): 55–70. doi:10.1177/0959354308101419.
- Millon, Theodore; Carrie M. Millon, Seth Grossman, Sarah Meagher, Rowena Ramnath (2004). Personality Disorders in Modern Life. John Wiley and Sons. p. 290. ISBN 0-471-23734-5.
- Millon, Theodore (2006). "Personality Subtypes Summary". The Official Website for Theodore Millon, Ph.D., D.Sc. DICANDRIEN, Inc. Retrieved January 22, 2010.
- Paul Babiak, Robert D. Hare. Snakes in Suits: When Psychopaths Go to Work year = 2007.
- Millon, Theodore. Disorders of Personality: DSM-IV and Beyond year = 1995.
- Theodore Millon, a Student of Personality, Dies at 85, The New York Times, January 31 2014.