The referendum resulted in 92% of valid votes in support of the bill on a turnout of 67%.

The feat of creating a democratic system without breaking the structures of power of the state was made possible by the approval of the Political Reform Act of 1977, passed by the Francoist Cortes as the last Fundamental Law.

The law provided for the legalization of political parties and a democratic election to Constituent Cortes, a committee of which then drafted the Constitution.

[5] Adolfo Suárez's government had lowered voting age from 21 to 18 only three weeks before the referendum, which resulted in a made-up electoral register increasing by over 3 million people compared to the 1977 general election amid technical, administrative and logistical issues.

[6] Interior Ministry officials acknowledged deviations of up to 5.1 per 100 in the electoral census—roughly 1.5 million people according to the National Institute of Statistics—resulting from the absence of an official electoral register and in an overreliance on data from municipal registers.