In 2004, when he was 20 years old, Tarrio was convicted of theft. He was sentenced to community service and three years of probation and was ordered to pay restitution. In 2013, Tarrio was sentenced to 30 months (of which he spent 16) in federal prison for rebranding and reselling stolen medical devices.
After 2004, Tarrio relocated to a small town in North Florida to run a poultry farm. He later returned to Miami. He has also founded a security equipment installation firm and another providing GPS tracking for companies.
Tarrio owns a Miami T-shirt business, known as the 1776 Shop, an online vendor for right-wing merchandise.Slate described the 1776 Shop as a "freewheeling online emporium for far-right merch" that sells a range of Proud Boys gear including shirts stating "Pinochet did nothing wrong".
Tarrio volunteered at a Miami event for far-right commentator Milo Yiannopoulos in May 2017 where he encountered a member of the Proud Boys who encouraged him to join the group. In August 2017, Tarrio attended the Unite the Right rally in Charlottesville, Virginia. His stated reason for his presence was to protest against the removal of Confederate statues.
Tarrio became a fourth-degree member of the Proud Boys, a distinction reserved for those who get into a physical altercation, after punching someone who is believed to be aligned with antifa in the face in June 2018. He assumed the role of chairman for the organization on November 29, 2018, succeeding Jason Lee Van Dyke, who held the position for two days, and Van Dyke's predecessor Gavin McInnes.
Tarrio was arrested by Washington, D.C. police on January 4, 2021 and charged with one misdemeanor count of destruction of property. According to a police spokesperson, this was in connection to the burning of a Black Lives Matter banner stolen from a Washington, D.C. church during a pro-Trump march on December 12, 2020 that drew around 200 Proud Boys. Tarrio was also charged with two felony counts of possession of a high capacity feeding device after two high-capacity firearms magazines were found on Tarrio when he was arrested. A statement released by African Methodist Episcopal Church, which was one of two historically black churches targeted during the December 12 D.C. protest, also revealed that the church had filed a lawsuit against both Tarrio and Proud Boys organization. After his release on January 5, 2021, Tarrio was banned from entering Washington, DC, except for trial or meeting with his lawyers. 
In regard to his views on extremist groups and ideologies, Tarrio has been quoted as saying, "I denounce white supremacy. I denounce anti-Semitism. I denounce racism. I denounce fascism. I denounce communism and any other -ism that is prejudiced towards people because of their race, religion, culture, tone of skin." In regard to his own ethnicity, he has said, "I'm pretty brown, I'm Cuban. There's nothing white supremacist about me."
In 2018, Twitter removed Tarrio's account, amongst others related to the Proud Boys, citing how platform policy prohibited accounts related to violent extremist groups. The following year, another account created by Tarrio to evade the suspension was detected and removed from the platform by Twitter.
Tarrio is a close friend of Roger Stone. After Stone was arrested in January 2019, Tarrio appeared outside the courtroom in a shirt emblazoned with the message "Roger Stone did nothing wrong".
Tarrio began a run for Congress for Florida's 27th district in 2020, but withdrew before the Republican Party primary. In his campaign's responses to a Ballotpedia survey done in 2019, Tarrio listed criminal justice reform, protection of the Second Amendment, countering domestic terrorism, ending the war on drugs, free speech on digital platforms, and immigration reform among some of his priorities.
HoSang, Daniel (2019). Producers, Parasites, Patriots: Race and the New Right-Wing Politics of Precarity. University of Minnesota Press. p. 2. ISBN9781452960340. [...] groups such as the protofascist Proud Boys [...].
Álvarez, Rebecca (2020). Vigilante Gender Violence: Social Class, the Gender Bargain, and Mob Attacks on Women Worldwide. Routledge. ISBN978-1000174137. The Proud Boys are a neo-fascist masculinist hate group.
"Proud Boys". Southern Poverty Law Center. Archived from the original on October 16, 2018. Retrieved October 16, 2018.
Lowry, Rich (October 19, 2018). "The Poisonous Allure of Right-Wing Violence". National Review. Archived from the original on October 22, 2018. Retrieved November 13, 2018. McInnes is open about his glorification of violence. In a speech, he described a clash with Antifa outside a talk he gave at NYU last year: 'My guys are left to fight. And here's the crucial part: We do. And we beat the crap out of them.' He related what a Proud Boy who got arrested told him afterward: 'It was really, really fun.' According to McInnes: 'Violence doesn't feel good. Justified violence feels great. And fighting solves everything.'
^Coaston, Jane (October 15, 2018). "The Proud Boys, explained". Vox. Archived from the original on October 3, 2020. Retrieved October 2, 2020. became a fourth-degree Proud Boy after punching a purported member of antifa in the face in June 2018.