Marjolein Sieczkowski, LCSW
Clinical Social Worker · Flagstaff, AZ
Marjolein Sieczkowski, LCSW is a clinical social worker with a practice address in Flagstaff, Arizona, and NPI 1457850984, issued on Feb 10, 2018. Check the license (Arizona LCSW-16963, as entered in NPPES) with the Arizona board that licenses this profession; the Medicare figures below come from public CMS files.
- Name
- Marjolein Sieczkowski
- Credential
- LCSW
- Primary taxonomy
- Clinical Social Worker 1041C0700X
- License number
- LCSW-16963 AZ
Self-reported in NPPES; status is on the state search - Practice location
- 125 E Elm Ave Ste 203, Flagstaff, AZ 86001
- Phone
- (480) 466-2428
- Enumerated
- Feb 10, 2018
- Record last updated
- Feb 10, 2018 (not updated in 8 years: call before relying on the address or phone)
- Medicare enrollment
- Enrolled (PECOS I20180425000765); accepts Medicare assignment
- Entity
- Type 1 · individual
8 nearest clinical social worker records → All 3,200 in Arizona → Look up another NPI →
Verify Marjolein Sieczkowski in five checks
- 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
- 2LicenseActive license and public ordersWhich Arizona board licenses this profession
Search for license LCSW-16963Check 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
- Kelli Sieczkowski PLLCMesa, AZ
Source: CMS Doctors and Clinicians National Downloadable File (the group practices a clinician bills Medicare through) (data.cms.gov).
Marjolein Sieczkowski among 3,200 clinical social worker records in Arizona
Marjolein Sieczkowski, LCSW is one of 3,200 clinical social worker records with a practice address in Arizona. 11% of them appear in a Medicare file (Part D prescribing, MIPS, Open Payments or Medicare group billing); this one does. Its NPI, issued in 2018, is newer than 55% of them.
- NPI issued2018 · 55% of these records are older, 41% newer
- In a Medicare fileYes · 11% of these records are
- In the CMS Doctors and Clinicians fileYes · 20% of these records are
- Graduated2009 · median 2011 among the 648 with a school on file
- Record last updated2018 · 47% of these records were not updated in five years or more
Source: CMS NPPES, file of Aug 9, 2026, every record with primary taxonomy 1041C0700X and a Arizona practice address; Medicare files: CMS Part D Prescribers 2024, MIPS 2023, Open Payments 2024, Doctors and Clinicians (data.cms.gov).
81 clinical social worker records list a practice address in Flagstaff
They are 81 of the 2,419 NPPES records with a practice address in Flagstaff, and 3,200 clinical social worker records in Arizona.
All 3,200 in Arizona → Every provider in Flagstaff → Clinical Social Worker nationwide →
The 8 clinical social worker records with the nearest ZIP codes
- Deborah Bennett, M.S.W.Flagstaff, AZ 860011720091093
- Susan Boness, MSWFlagstaff, AZ 860011326298134
- Sara Codner, MSSW, LCSWFlagstaff, AZ 860011831428259
- Cristina Culhane, LCSWFlagstaff, AZ 860011619115359
- Craig Davis, LCSWFlagstaff, AZ 860011225278930
- April Ely, LCSWFlagstaff, AZ 860011659642759
- Vickey Finger, MSWFlagstaff, AZ 860011518944701
- Lauren Fofanova, LCSWFlagstaff, AZ 860011164743613
Common questions
What is Marjolein Sieczkowski, LCSW's NPI number?
Marjolein Sieczkowski, LCSW's National Provider Identifier (NPI) is 1457850984, issued on Feb 10, 2018. An NPI identifies a provider in billing; it is not a license.
Where is Marjolein Sieczkowski, LCSW located?
The NPPES record lists a practice address at 125 E Elm Ave Ste 203, Flagstaff, AZ, 86001. Phone: (480) 466-2428. Providers update this record themselves, so call before visiting.
How can I verify Marjolein Sieczkowski, LCSW's license?
NPPES lists Arizona license number LCSW-16963, as entered by the provider. Search the Arizona 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.