[2] Montero joined Podemos after the elections to the European Parliament in 2014 together with Rafa Mayoral from the Platform of People Affected by Mortgages (PAH).

Since 18 February 2017 she has held the position of Spokesperson[4] of the United Confederal Group We Can-In Comú Podem-En Marea, being the youngest speaker of democracy.

[8] In May 2018, Iglesias and Montero put their positions in Podemos up for a vote of no confidence, following backlash for purchasing a €615,000 country house in Galapagar.

During her time in office, she oversaw the government's efforts on a bill to allow anyone over the age of 14 to change gender legally without a medical diagnosis or hormone therapy.

[13] In August 2022, Spain passed legislation proposed by Montero since the La Manada rape case, in which consent for sexual intercourse had to be proven by affirmation.

[17] The law was amended in April 2023 by the PSOE and opposition PP, which Montero considered "a sad day" and the most difficult of her tenure as a minister.

On 3 July 2018, Montero gave birth to twins, Leo and Manuel, in her relationship with Pablo Iglesias, the leader of her party.

The court ordered Montero to pay €18,000 in compensation to the plaintiff, delete a tweet in which she shared a video of the opening ceremony of the Women's Institute where she made the statements for which she was convicted, and post the judgment on Twitter.

[26] In September, Montero appealed to a higher court, on the grounds that the judgment would erode her credibility and violate her free speech.