The measure will affect those living in Spain for at least five months and who applied for international protection before 31 December 2025.
Spain's left-wing government approved a plan on Tuesday to regularise around 500,000 undocumented migrants by decree, the country's latest break with harsher policies elsewhere in Europe.
Migration Minister Elma Saiz the beneficiaries would be able to work "in any sector, in any part of the country" and extolled "the positive impact" of migration.
"We are talking about estimations, probably more or less the figures may be around half a million people," she told public broadcaster RTVE.
Saiz said at a news conference after Tuesday's cabinet meeting that "we are strengthening a migration model based on human rights, integration, coexistence and compatible with economic growth and social cohesion."
The measure will affect those living in Spain for at least five months and who applied for international protection before 31 December 2025.
Applicants must have a clean criminal record. The regularisation will also apply to their children who already live in Spain.
The application period is expected to open in April and continue until the end of June.
The plan will be passed through a decree that will not need approval in parliament, where the Socialist-led coalition lacks a majority.
The conservative and far-right opposition lashed out at the government, saying the regularisation would encourage more illegal immigration.
Alberto Nunez Feijoo, head of the Popular Party, the main right-wing opposition group, wrote on X that the "ludicrous" plan would "overwhelm our public services."
"In Socialist Spain, illegality is rewarded," he said, vowing to change migration policy "from top to bottom" if he took power.
'Social justice'
The Spanish Catholic Church was among the organisations praising the move, commending "an act of social justice and recognition."
Socialist Prime Minister Pedro Sánchez says Spain needs migration to fill workforce gaps and counteract an ageing population that could imperil pensions and the welfare state.
Sánchez has said migration accounted for 80% of Spain's dynamic economic growth in the last six years.
Official data released on Tuesday showed that 52,500 of the 76,200 people who pushed up employment numbers in the final quarter of last year were foreigners, contributing to the lowest jobless figure since 2008.
Spain's more open stance contrasts with a trend that has seen governments toughen migration policies under pressure from far-right parties that have gained ground across the European Union.
Around 840,000 undocumented migrants lived in Spain at the beginning of January 2025, most of them Latin American, according to the Funcas think-tank.
Spain is one of Europe's main gateways for irregular migrants fleeing poverty, conflict and persecution, with tens of thousands of mostly sub-Saharan African arrivals landing in the Canary Islands archipelago off northwestern Africa.
According to the latest figures published by the National Statistics Institute, more than 7 million foreigners live in Spain out of a total population of 49.4 million people.