Short answer: ISO 27001 and CMMC Level 2 share a security-management mindset and overlap on roughly 60–70% of controls, but DoD does not accept ISO 27001 as a substitute for CMMC. The gaps that matter: ISO is risk-driven (you pick the controls), CMMC mandates all 110 NIST 800-171 controls; ISO has no equivalent of FedRAMP Moderate cloud hosting, 72-hour DFARS reporting, or FIPS 140-validated crypto requirements. Existing ISO 27001 work is valuable input — not an output you can hand to a C3PAO.
Side-by-side comparison
- Scope: ISO 27001 covers any information asset; CMMC Level 2 specifically protects CUI in the defense supply chain.
- Control selection: ISO is risk-based — you justify which Annex A controls apply. CMMC requires all 110 NIST 800-171 controls, period.
- Assessment cadence: ISO surveillance audits annually, recertify every 3 years. CMMC is a 3-year certificate with annual self-attestation.
- Cloud requirements: ISO is silent on hosting. CMMC requires FedRAMP Moderate (or Moderate Equivalent) for CSPs handling CUI.
- Incident reporting: ISO requires you to have a process. CMMC mandates 72-hour reporting to DIBNet.
Where they overlap
If you're ISO 27001 certified, you've largely solved:
- Risk assessment process (NIST 800-171 §3.11)
- Access control basics (§3.1)
- Awareness training (§3.2)
- Asset inventory and configuration baselines (§3.4)
- Incident response plan structure (§3.6)
- Audit log retention policy (§3.3)
Where ISO falls short for DoD
- FedRAMP cloud hosting for CUI — must use GCC High, AWS GovCloud, Azure Government, or equivalent. Commercial M365 or AWS Commercial does not satisfy the underlying CSP requirement.
- FIPS 140-2/3 validated cryptography for CUI at rest and in transit. ISO allows any "adequate" crypto.
- DFARS 252.204-7012 72-hour incident reporting to DIBNet, with media preservation for 90 days.
- US persons only for systems handling export-controlled CUI (no offshore admins, even with NDAs).
- SPRS score posted to a DoD portal — no ISO equivalent.
- Specific control depth — e.g. CMMC requires session lock at 15 minutes and FIPS-validated key management, which ISO leaves to your risk decision.
How to leverage existing ISO work
- Map your ISO Statement of Applicability to the 110 NIST 800-171 controls — most ISO ISMS evidence (policies, training records, risk register) can be cited in your SSP.
- Use the ISO incident management process as the bones of your DFARS 7012 runbook; add the DIBNet filing + 90-day media preservation steps.
- Carve a separate CMMC scope around CUI workloads — don't try to certify your whole ISO scope at Level 2 (cost explodes).
- Pick a C3PAO that has done ISO-to-CMMC mappings before; they'll save you weeks of re-papering.
Mentioned in this guide
Frequently asked questions
- Will my ISO certificate satisfy a prime?
- Sometimes for risk-screening purposes, but not for DFARS 7012 / CMMC contract clauses. If the contract requires CMMC Level 2, you need a C3PAO certificate, not ISO.
- Can I get both ISO 27001 and CMMC Level 2 from one auditor?
- Rarely — accreditation bodies are different (ANAB for ISO, Cyber AB for CMMC). Some firms hold both authorizations but you still get two separate assessments.
- Is SOC 2 closer to CMMC than ISO?
- Comparable. SOC 2 Type II overlaps on access controls, change management, and monitoring, but has the same gaps as ISO around FedRAMP hosting, DFARS reporting, and FIPS crypto.
- What about NIST CSF?
- NIST CSF is a framework, not a control catalog. CMMC Level 2 specifically requires NIST 800-171 r2 controls. CSF maturity work is useful background but not a substitute.
Related guides
- CMMC Level 1 vs Level 2: Which Do You Actually Need?CMMC Basics · 7 min read
- NIST 800-171: All 110 Controls in Plain EnglishControls · 12 min read
- CMMC 2.0 Cost and Timeline for Small Defense Contractors (2026)Cost & Timeline · 10 min read
- System Security Plan (SSP) Template for Small Defense ContractorsSSP · 11 min read