Where the two genuinely overlap
GDPR Article 32 requires security appropriate to the risk, explicitly mentioning measures like pseudonymization, encryption, resilience, and regular testing. A certified ISO 27001 ISMS is close to the best available evidence of exactly that: risk-driven control selection, operating evidence, independent audit. Regulators and courts assessing whether your security was "appropriate" after an incident look far more kindly on a certified, operating ISMS than on ad hoc measures. Certification also answers the security sections of processor due diligence under Article 28.
What GDPR requires that ISO 27001 never touches
- Lawfulness and purpose: a legal basis for each processing purpose, purpose limitation, data minimization.
- Data subject rights: access, rectification, erasure, portability, objection, with deadlines and processes.
- Transparency: privacy notices that actually describe your processing.
- Accountability artifacts: records of processing activities (Article 30), data protection impact assessments where required, processor contracts, and in some cases a Data Protection Officer.
- Breach notification: the 72-hour supervisory authority clock and data subject notification duties.
- International transfers: transfer mechanisms and assessments ISO 27001 knows nothing about.
The practical architecture that works
Treat ISO 27001 as the security engine and build privacy on top of the same machinery: extend the risk register with privacy risks, extend asset inventory into a record of processing, route data subject requests and breach response through the same incident and corrective processes, and let internal audit cover both. Organizations that run security and privacy as one management system with two lenses spend less and answer regulator and customer questions faster than those running parallel programs.
The sentence for your sales team
Say "our information security is ISO 27001 certified, which supports our GDPR Article 32 obligations", never "we are GDPR compliant because we are ISO 27001 certified". The first is accurate and impressive; the second is false and, to an informed buyer or regulator, self-discrediting.