What is a C3PAO? CMMC Third-Party Assessors Explained
A C3PAO is the only organization authorized to give you an official CMMC Level 2 certification. There are about 100 of them for 100,000+ contractors - which is exactly why Phase 2 was suspended. Here is everything you need to know about how they work and what an assessment looks like.
When CMMC first launched, the question "what is a C3PAO?" was mostly asked by defense contractors who had just received a contract requirement they did not recognize. Now, with Phase 2 suspended and the program under review, the question carries a different weight: understanding what C3PAOs are, what they do, and why they matter tells you a lot about why Phase 2 ran into trouble - and what any restructured program will still need to accomplish.
The Short Version
A C3PAO is a Certified Third-Party Assessment Organization - a company authorized by the Cybersecurity Maturity Model Certification Accreditation Body (Cyber AB) to conduct official CMMC Level 2 assessments. When CMMC Phase 2 requires a third-party assessment, the assessment must be conducted by a C3PAO. You cannot hire just any cybersecurity consultant - they must be a C3PAO.
That ratio - 100 authorized assessors for 100,000+ contractors - is one of the primary reasons Phase 2 was suspended. The math genuinely does not work, and the DoD acknowledged it.
The Cyber AB Ecosystem: C3PAOs, RPOs, and RPAs
The CMMC ecosystem has several types of authorized organizations that are easy to confuse. Here is how they differ:
| Role | What They Do | Can Conduct Official Assessment? |
|---|---|---|
| C3PAO Certified Third-Party Assessment Organization | Conducts official CMMC Level 2 assessments that result in a certification. Employs Certified CMMC Assessors (CCAs). | Yes - this is their sole purpose |
| RPO Registered Practitioner Organization | Provides CMMC consulting, gap assessments, remediation support, and documentation help. Cannot conduct official assessments. | No |
| RPA Registered Practitioner Advanced | Individual CMMC consultant with advanced Cyber AB credentials. Works through an RPO or independently. | No |
| CCA Certified CMMC Assessor | Individual assessor employed by a C3PAO who conducts the actual assessment activities. | Only when employed by a C3PAO |
| DIBCAC Defense Industrial Base Cybersecurity Assessment Center | DoD government organization that conducts High-confidence government-led assessments for the most sensitive programs. | Yes - government assessments only |
The practical implication: if someone tells you they can do your "CMMC certification" but they are an RPO, not a C3PAO, they can help you prepare for an assessment - but they cannot give you the certification. You will still need a C3PAO when Phase 2 requires it.
What the C3PAO Assessment Process Looks Like
A CMMC Level 2 assessment is not a questionnaire you fill out. It is a structured review process conducted over days or weeks by trained assessors. Here is roughly how it works:
Pre-Assessment / Scoping
The C3PAO reviews your System Security Plan and scopes the assessment. They establish which systems, locations, and personnel are in scope for CUI handling. Scoping errors here cost money - everything in scope gets assessed.
Document Review
Assessors review your SSP, policies, procedures, and evidence packages before the on-site visit. Gaps in documentation are flagged before the assessment begins. This is where being well-documented pays off - assessors make preliminary judgments from your documents.
Assessment Activities
On-site (or remote) assessment of technical controls: configuration reviews, system demonstrations, interview of key personnel, testing of specific practices. Assessors use NIST SP 800-171A as their guide - it defines exactly how each practice is assessed.
Draft Findings
The C3PAO produces a draft assessment report. You have an opportunity to provide additional evidence for any practices marked as "Not Met." This is your chance to produce evidence you missed in the document review phase.
Final Report and Score
The final report is submitted to CMMC eMASS. If all 110 practices are Met, you receive a CMMC Level 2 certification. Practices marked Not Met go on your POA&M with remediation timelines. Final disposition determines whether conditional certification is possible.
How to Find an Authorized C3PAO
The Cyber AB maintains the official marketplace at cybermarketplace.com. This is the authoritative source - if an organization is not listed there as a C3PAO, they are not authorized to conduct Level 2 assessments. Do not take anyone's word for it. Check the marketplace.
When evaluating C3PAOs, ask:
- How many Level 2 assessments have they completed? (The market is young - most have done few)
- Do they have experience in your industry or contract type?
- What is their current scheduling availability and estimated lead time?
- What is included in the assessment cost vs. billed separately?
- Do they offer a pre-assessment gap review, or only the formal assessment?
What About During the Phase 2 Pause?
While Phase 2 is suspended, mandatory C3PAO assessments are not required for new contracts. However:
- Contractors who need to demonstrate cybersecurity posture to a prime or contracting officer can still voluntarily obtain a C3PAO assessment
- Your SPRS self-assessment score is still required and still subject to False Claims Act scrutiny
- When Phase 2 resumes - in whatever restructured form the Task Force recommends - C3PAO capacity will still be a bottleneck. Getting on a C3PAO's schedule early is a competitive advantage
The capacity problem has not been solved. The Phase 2 pause paused the mandate, not the assessor shortage. When the requirement returns, there will still be far more contractors than available C3PAOs. Organizations that are prepared will have shorter assessment timelines and lower costs than those scrambling to catch up.
Preparing for a C3PAO Assessment?
The CMMC Level 2 Certification Kit gives you everything assessors will ask for: SSP, POA&M, and all 12 domain policies. Start building your evidence package now.
View the Certification Kit - $299