Dennis S. O'Brien, PAC
Medical Physician Assistant · Springfield, MA
Dennis S. O'Brien, PAC is a medical physician assistant with a practice address in Springfield, Massachusetts, and NPI 1407895956, issued on Jun 6, 2006. Check the license (Massachusetts PA4779, as entered in NPPES) with the Massachusetts board that licenses this profession; the Medicare figures below come from public CMS files.
- Name
- Dennis S. O'Brien
- Credential
- PAC
- Primary taxonomy
- Medical Physician Assistant 363AM0700X
- License number
- PA4779 MA
Self-reported in NPPES; status is on the state search - Practice location
- 3300 Main St, Springfield, MA 01199
- Phone
- (413) 794-7033
- Enumerated
- Jun 6, 2006
- Record last updated
- Dec 16, 2019 (not updated in 7 years: call before relying on the address or phone)
- Fax
- (413) 794-7297
- Medicare enrollment
- Enrolled (PECOS I20140131000250); accepts Medicare assignment
- Entity
- Type 1 · individual
8 nearest medical physician assistant records → All 886 in Massachusetts → Look up another NPI →
Also registered at 3300 Main St
A shared address usually means a shared clinic or building; it does not show who employs whom.
- Octavian Adam, M.D.Neurology Physician1104020791
- Nancy Allen, NPAdult Health Nurse Practitioner1063510261
- Andrew Artenstein, MDInfectious Disease Physician1316995277
- Jessica Bean Jaworski, PHDPsychologist1821473091
- Laurie Beauchemin, CNMAdvanced Practice Midwife1801125133
- Kristin Chaplin, PA-CMedical Physician Assistant1184032898
Verify Dennis S. O'Brien in five checks
- 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
- 2LicenseActive license and public ordersWhich Massachusetts board licenses this profession
Search for license PA4779Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
Bills Medicare through one group practice
- Baystate Medical Practices IncSpringfield, MA
Source: CMS Doctors and Clinicians National Downloadable File (the group practices a clinician bills Medicare through) (data.cms.gov).
Dennis S. O'Brien among 886 medical physician assistant records in Massachusetts
Dennis S. O'Brien, PAC is one of 886 medical physician assistant records with a practice address in Massachusetts. 78% of them appear in a Medicare file (Part D prescribing, MIPS, Open Payments or Medicare group billing); this one does. Its NPI, issued in 2006, is newer than 2% of them.
- NPI issued2006 · 2% of these records are older, 78% newer
- In a Medicare fileYes · 78% of these records are
- In the CMS Doctors and Clinicians fileYes · 63% of these records are
- Graduated2004 · median 2015 among the 559 with a school on file
- Record last updated2019 · 53% of these records were not updated in five years or more
Source: CMS NPPES, file of Aug 9, 2026, every record with primary taxonomy 363AM0700X and a Massachusetts practice address; Medicare files: CMS Part D Prescribers 2024, MIPS 2023, Open Payments 2024, Doctors and Clinicians (data.cms.gov).
182 medical physician assistant records list a practice address in Springfield
They are 182 of the 8,553 NPPES records with a practice address in Springfield, and 886 medical physician assistant records in Massachusetts.
All 886 in Massachusetts → Every provider in Springfield → Medical Physician Assistant nationwide →
The 8 medical physician assistant records with the nearest ZIP codes
- Suzanne Arnopolin, PA-CSpringfield, MA 011991306952718
- Stephen Burgess, PA-CSpringfield, MA 011991053412106
- Heidi-Ann Courtney, PASpringfield, MA 011991750316873
- Patricia Dauley, PA-CSpringfield, MA 011991578533501
- Louis Favata, PA-CSpringfield, MA 011991518947159
- Rebecca Fisher, PA-CSpringfield, MA 011991881601516
- Bethany Foster, PA-CSpringfield, MA 011991851377964
- Annemarie Legrand, PA-CSpringfield, MA 011991215037767
Common questions
What is Dennis S. O'Brien, PAC's NPI number?
Dennis S. O'Brien, PAC's National Provider Identifier (NPI) is 1407895956, issued on Jun 6, 2006. An NPI identifies a provider in billing; it is not a license.
Where is Dennis S. O'Brien, PAC located?
The NPPES record lists a practice address at 3300 Main St, Springfield, MA, 01199. Phone: (413) 794-7033. Providers update this record themselves, so call before visiting.
How can I verify Dennis S. O'Brien, PAC's license?
NPPES lists Massachusetts license number PA4779, as entered by the provider. Search the Massachusetts board that licenses this profession; the NPPES record confirms identity only.
Source: CMS National Plan and Provider Enumeration System (NPPES), file of Aug 9, 2026 (NPPES files on CMS.gov); NUCC Health Care Provider Taxonomy. Medicare files from data.cms.gov. An NPI identifies who bills; it is not a license.
Figures on PlainDoctor are read from the federal files each page names (CMS NPPES, Medicare Part D, MIPS, Open Payments; the HHS-OIG exclusion list only as counts) and from Census population estimates, with the file date shown beside them. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of Aug 9, 2026.