Provider records sourced from NPPES (CMS National Plan & Provider Enumeration System). Data current as of August 10, 2026.

Dr. James John O'Leary, MD

Individual provider Medical Oncology Physician · NPI 1336371012

Dr. James John O'Leary, MD is a Medical Oncology Physician in Waltham, Massachusetts. Practices as a sole proprietor. Licensed in New York.

Licensed in
NY
In the registry since
2009
What do these letters mean?
MD — Doctor of Medicine
A physician who completed allopathic medical school.

See every abbreviation used in this directory →

Practice location Address checks out

830 Winter St
Waltham, MA 02451-1477
Phone: (781) 895-0600
Fax: (781) 895-0611
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Pin is approximate — placed at the ZIP-code centre, not the exact door.

Specialties & licences

Medical Oncology Physician (primary) Taxonomy 207RX0202X · Licence 188142 (NY)

Record details

NPI number1336371012
Entity typeIndividual (Type 1)
GenderMale
Credentials MD
Sole proprietorYes
NPI enumeratedAugust 14, 2009
Last updated in NPPESAugust 14, 2009
Mailing address830 Winter St, Waltham, MA 02451-1477

Other providers in Waltham