Alejo Vidal Quadras, 78, was rushed to hospital in serious condition, but is expected to survive.
According to El País, the incident took place around 1:30pm on Núñez de Balboa Street in the capital's Salamanca neighborhood, where Vidal Quadras lives.
The attackers, one of whom was described by witnesses as a "young, small man" wearing a motorcycle helmet, allegedly shot the politician in the jaw after "loitering" near his home.
Following the attack, he fled on a motorcycle, and has not yet been apprehended.
Vox Party President Santiago Abascal said it was "too early to make conjectures," but noted that they "don't rule out any motive in what was an attack."
"I want to convey my solidarity and wishes for a speedy recovery to Alejo Vidal-Quadras," socialist acting prime minister Pedro Sanchez said in a post on X.
"All my affection at this time for him and his family. We trust that the investigation can clarify the facts as soon as possible and those responsible will be arrested."
It has been claimed that Vidal-Quadras was on his way to "protest against the Sanchez government’s decision to issue an amnesty for separatist leaders."
As the BBC reports, Right-wing protestors have taken to the streets in cities across the country this week to voice their opposition to a new law that would grant amnesty to Catalan politicians and activists involved in the region's failed attempt to separate from Spain in 2017.
The push to grant amnesty could seal a win for Sanchez, who came in second during the recent federal elections, but could become prime minister as the Popular Party fails to form a coalition.
Vidal-Quadras sat as a member of the European Parliament for the "neoconservative Popular Party from 1999 to 2014, and also served as the EP's first vice president from 2004 to 2007. He left the party in 2014 to co-found the Vox party, which bills itself as more right-wing, but has been deemed "far-right" by many over its stance on immigration and desire for centralization of the state.
After failing to win a seat in the EP with his new party, Vidal-Quadras left his position in Vox as well, and went on to operate a Brussels-based lobby in opposition to the Iranian government.
This is a breaking story and will be updated.