A C3PAO — CMMC Third-Party Assessment Organization — is the independent company authorized to conduct the certification assessments that CMMC Level 2 requires for most CUI-handling contracts. They are accredited under the CMMC ecosystem that 32 CFR Part 170 establishes, and listed on the Cyber AB Marketplace. If Level 2 certification is in your future, a C3PAO is who certifies you — so it pays to understand what they do, what they cannot do, and how the engagement works.
What a C3PAO actually does
A C3PAO fields the certified assessment team that examines your implementation of the 110 NIST SP 800-171 requirements against their roughly 320 assessment objectives — by examining artifacts, interviewing your people, and testing systems. The assessment is conducted against your System Security Plan, scored on the DoD methodology, and results in a certification decision (full or conditional with a 180-day POA&M closeout). The engagement typically spans planning and evidence exchange, an assessment week, and adjudication.
C3PAO vs. RPO vs. RP — who does what
- C3PAO: assesses and certifies. Independent by design.
- RPO (Registered Provider Organization): consults, prepares, implements — the coach, not the referee. CLOUD2E is an RPO.
- RP (Registered Practitioner): an individual credentialed on the CMMC method, typically working under an RPO.
Finding and choosing one
Start at the Cyber AB Marketplace — the authoritative list of authorized C3PAOs. Selection factors that matter in practice: assessment calendar availability (good teams book out months), experience with your environment pattern (cloud enclave vs. on-prem, GCC High tenancy, OT on the floor), industry familiarity, and how they run evidence exchange. Price varies with your scope — fewer in-scope assets and cleaner documentation genuinely cost less to assess, which is one more return on tight scoping. For market cost context, see the figures and sources in our Level 2 cost guide.
Being ready when they arrive
C3PAOs certify what exists — readiness is your job (and ours, for our clients). The preparation sequence is the compliance checklist: scope, remediate, document, self-assess against 800-171A, then rehearse. The body of evidence should be organized before the planning call, interviewees should know their own procedures, and the assessment-week walkthrough on this site covers what the days feel like. Contractors who treat the assessment as a verification of a running program pass; contractors who treat it as a deadline to assemble one, struggle.