To evaluate electronic cigarette (e-cigarette) product compliance with European regulations (Tobacco Products Directive (TPD), Implementing Decisions), with a focus on labelling/packaging practices and technical design/safety features.Before the implementation of the TPD, in early 2016, we randomly selected e-cigarette refill liquids from the five top-selling companies in France, Poland, Germany, Netherlands, UK, Spain, Romania, Hungary and Greece. Identical products were purchased after the implementation of the TPD (early 2018) and assessment of compliance was performed on self-matched samples (n=107) using a prospective cohort design. Compliance with the Classification, Labelling and Packaging (CLP) regulations was also evaluated.Following the implementation of the TPD, improvements were noted with regards to the existence of text-only warnings (32.7% pre vs 86.0% post, p<0.001), child-resistant fastenings (93.3% pre vs 100.0% post, p=0.016), tamper-proof vials (58.9% pre vs 86.9%, post p<0.001) and maximum refill volume ≤10 mL in vials (86.9% pre vs 94.4% post, p=0.008). Lower compliance was noted with regards to the inclusion of a leaflet (26.2% pre vs 53.3% post, p<0.001), refilling instructions (28.0% pre vs 51.4% post, p<0.001) and health warnings on the box, vial or leaflet (32.7% pre vs 86.0%, p<0.001). Overall, 86.0% of products had a warning label in the post-TPD phase in comparison to 32.7% of products before the implementation of the TPD (p<0.001). Compliance with the CLP regulations, also increased in the post TPD follow-up phase.This is the first study to evaluate the level of implementation of the e-cigarette regulations in nine EU member states. Our results indicate that refill liquids had substantial but not full compliance in most of the characteristics evaluated. Further effort is needed to ensure complete compliance.