"It is proof that diplomacy works and delivers... The European Union will continue to work for the respect and implementation of this extremely important deal, most of all for our security," Mogherini said on Monday, AFP reported.
She made the remarks on the first anniversary of coming into force of the Joint Comprehensive Plan of Actions (JCPOA) between Tehran and the Group 5+1 (Russia, China, the US, Britain, France, and Germany).
They reached the nuclear agreement in July 2015 and implemented it in January last year.
The agreement "has delivered both on the nuclear-related commitments Iran took and on the firm determination of the international community to fully implement this deal", she added.
As far as the EU was concerned, the accord had resulted in increased trade and economic ties, "which is really significant", Mogherini further said.