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

Individual provider Clinical Social Worker · NPI 1457850984

Marjolein Sieczkowski, LCSW is a Clinical Social Worker in Flagstaff, Arizona. Qualified in 2009, 17 years ago. Practices with Kelli Sieczkowski PLLC, a 2-clinician group and accepts Medicare assignment. Licensed in Arizona.

Years since qualifying
17
Licensed in
AZ
In the registry since
2018
What do these letters mean?
LCSW — Licensed Clinical Social Worker
A social worker licensed to diagnose and treat mental health conditions independently.

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Practice location Address checks out

125 E Elm Ave Ste 203
Flagstaff, AZ 86001-3261
Phone: (480) 466-2428
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Pin is approximate — placed at the ZIP-code centre, not the exact door.

Specialties & licences

Clinical Social Worker (primary) Taxonomy 1041C0700X · Licence LCSW-16963 (AZ)

Record details

NPI number1457850984
Entity typeIndividual (Type 1)
GenderFemale
Credentials LCSW
Sole proprietorYes
NPI enumeratedFebruary 10, 2018
Last updated in NPPESFebruary 10, 2018

Medicare enrollment

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

Medicare specialtyCLINICAL SOCIAL WORKER
Medical schoolOTHER
Graduated 2009 (17 years in practice)
Group practice Kelli Sieczkowski Pllc — 2 clinicians
Accepts Medicare assignment Yes — accepts the Medicare-approved amount

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