"I believe (the decision) was taken unanimously. There was no divergent opinion with relation to the communique of the decision taken in Vilnius two weeks ago," de Guindos said during a conference in Santander in the north of Spain.
On Tuesday, ECB Governor Mario Draghi hinted at new stimulus measures that had yet to be discussed by the ECB's Governing Council, while Reuters sources said rate setters had not expected such a strong message.
The ECB ruled out raising interest rates within the next year at the last monetary policy meeting in Vilnius, Lithuania on June 6.
At the meet, there had been two main issues, de Guindos said, including the extension of the forward guidance on when the bank would raise interest rates and the cost of the ECB's Longer-Term Refinancing Operation (TLTRO III).
"There was also unanimity in that, if the situation deteriorated because downside risks materialised, we would immediately react," de Guindos said.
On Tuesday, Draghi said the bank would ease policy again if euro zone inflation failed to accelerate closer to the bank's target of just below 2%.
(This story was refiled to correct typo in de Guindos' name in fifth paragraph)
(Reporting by Paul Day; Editing by Ingrid Melander and Toby Chopra)