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

William Charles O'Callahan Jr., MD

Individual provider Emergency Medicine Physician · NPI 1114964186

William Charles O'Callahan Jr., MD practises Emergency Medicine in Holden, Massachusetts. Graduated from University of Massachusetts Medical School in 1990, 36 years ago. Practices with Urgent Care Specialists PC, an 11-clinician group, works from 4 locations and accepts Medicare assignment. Licensed in Massachusetts.

Years since qualifying
36
Trained at
University of Massachusetts Medical School
Licensed in
MA
In the registry since
2006
What do these letters mean?
MD — Doctor of Medicine
A physician who completed allopathic medical school.

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Practice location Address checks out

5 Shrewsbury St Ste D
Holden, MA 01520-1960
Phone: (508) 829-3800
Fax: (508) 829-3802
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Pin is approximate — placed at the ZIP-code centre, not the exact door.

Additional practice locations (3)

  • 688 Bliss Road, Longmeadow, MA 01106-1534 — (413) 567-0011
  • 2040 Boston Road, Wilbraham, MA 01095-1380 — (413) 599-3800
  • 2040 Boston Rd Ste 5, Wilbraham, MA 01095-1380 — (413) 599-3800

Specialties & licences

Emergency Medicine Physician (primary) Taxonomy 207P00000X · Licence 79001 (MA)

Record details

NPI number1114964186
Entity typeIndividual (Type 1)
GenderMale
Credentials MD
Sole proprietorNo
NPI enumeratedMay 31, 2006
Last updated in NPPESJanuary 21, 2025
Certification dateJanuary 21, 2025

Medicare enrollment

From the CMS Doctors & Clinicians file — this clinician is enrolled in Medicare.

Medicare specialtyEMERGENCY MEDICINE
Medical schoolUNIVERSITY OF MASSACHUSETTS MEDICAL SCHOOL
Graduated 1990 (36 years in practice)
Group practice Urgent Care Specialists Pc — 11 clinicians
Accepts Medicare assignment Yes — accepts the Medicare-approved amount

Medicare patients and services, 2024

From the CMS Medicare Physician & Other Practitioners file for calendar year 2024. It counts Original Medicare patients only, so a practice that mostly sees Medicare Advantage or privately insured patients looks smaller here than it is.

Medicare patients511
Services billed 1,147 a service is one billed item, such as a visit, a test or a procedure
Average patient age74

Dollar amounts are not shown. What Medicare pays a practice is gross billings, before staff, premises and tax and including the cost of any drugs it administers, so it is not what a clinician earns.

Practises at

Facilities the CMS Facility Affiliation file lists for this clinician.

Colleagues at Urgent Care Specialists PC

Clinicians the CMS Doctors & Clinicians file lists under the same group practice. CMS counts 11 clinicians in the practice; 6 are shown here.

Other providers in Holden