Socialist Prime Minister Pedro Sanchez named 11 women to top posts including defence and economy in a cabinet with six male ministers.
That makes it the European government with the most women after Sweden's, which has 12 female cabinet ministers and 11 men.
Sanchez's administration risks not lasting until the end of the current mandate in 2020, however, given the fragmented state of Spain's political parties.
His Socialist Party holds just 84 seats in the 350-seat congress. That is the smallest parliamentary presence of any Spanish government since the return to democracy in the 1970s.
Sanchez, 46, ousted conservative veteran Mariano Rajoy as prime minister last Friday in a no-confidence vote.
The vote was sparked by corruption convictions against former officials from Rajoy's Popular Party (PP).
It ended more than six years of PP government and ushered in a progressive administration under Sanchez.
The swearing-in ceremony at the Zarzuela palace near Madrid broke with tradition by not involving a Bible, crucifix or other religious symbols.
Each new cabinet member vowed to "faithfully fulfil the duties of minister with conscience and honour".
EU budget manager Nadia Calvino became economy minister and former European parliament president Josep Borrell foreign minister.
The new executive includes two veteran Socialists -- Carmen Calvo, vice-president, and Borrell.
Calvo, who was culture minister from 2004 to 2007, will also be in charge of equality.
That is a priority for Sanchez's government in a country where women staged an unprecedented strike to defend their rights on March 8.
"This is a government that has to work every day for the most important thing of democracy: to reduce inequalities, and build the greatest equality, that between men and women," she said after being sworn in.
With its parliamentary minority, the government will rely on the votes of far-left party Podemos as well as Basque and Catalan nationalist lawmakers who supported his no-confidence motion.
Podemos leader Pablo Iglesias wished the new government "good luck".
He warned during an interview with public television channel TVE that his party would "influence from within parliament to change things. That is our job."
Podemos is pushing for greater social spending -- a delicate issue given the European Union's demands on budgetary discipline.
Spain has promised to reduce its deficit to 2.2 percent of GDP in 2018, which would bring it at last under the three percent limit set by Brussels.
To maintain "stability," Sanchez has also promised to implement the 2018 budget crafted by the previous conservative government.
That budget includes pensions hikes and a salary increase for civil servants.
The new Spanish executive's pro-EU credentials sets it apart from certain other parts of Europe.
They contrast with the eurosceptic stance of the populist government about to take office in Italy and the Brexit process in Britain.
Calvino's appointment as economy minister was welcomed by the EU Commission. Borrell was European parliament president between 2004 and 2007.
Anti-terror prosecutor Dolores Delgado became justice minister and former Supreme Court judge Margarita Robles defence minister.
Other women have been put in charge of education, employment and health.
The new interior minister is Fernando Grande-Marlaska, an openly gay former judge at Spain's top-level National Court.
He has handled cases against Basque separatist group ETA.
Borrell fiercely opposes the independence movement in his home region of Catalonia.
He will be tasked with defending abroad his government's commitment to Spanish unity.
Day to day, Meritxell Batet, another Catalan, has been put in charge of relations with Spain's regions.
She will have the prickly task of trying to ease the situation in her own deeply divided home region.
Sanchez's new team also includes a minister in charge of science, innovation and universities.
That role goes to Spain's first astronaut, Pedro Duque.
Maxim Huerta, an award-winning author, became culture minister.
Get the latest election news, live updates and election schedule for Lok Sabha Elections 2019 on ndtv.com/elections. Like us on Facebook or follow us on Twitter and Instagram for updates from each of the 543 parliamentary seats for the 2019 Indian general elections. Election results will be out on May 23.