Ramírez made his professional boxing debut at the age of 22 as a heavyweight on April 8, 2006, against 32-year-old Miguel Angel Pacheco at the Estadio Luna Park in Buenos Aires, Argentina.
Ramírez then fought three times in the space of five months at the Club El Porvenir in San Miguel del Monte, Buenos Aires winning all fights inside the distance against Roberto Martinez, Jose Norberto Gomez and Mario Javier Moreno.
Ramírez suffered his first defeat on his 7th fight in December 2006 against Sebastian Ignacio Ceballos via majority decision with judges scores of 56–59, 56–57 and 57½–57½.
Ramírez fought the undefeated Aleksandr Alekseyev (16–0, 15 KOs) at the Burg-Waechter Castello in Düsseldorf, Germany, on January 17, 2009, for the vacant interim WBO world cruiserweight title.
[1] Ramírez was promoted to full title holder and made his first defence against 35 year old Ali Ismailov in May 2009 in his native Argentina.
[2] It was announced that Ramírez would make his second defence on August 29, 2009, against former IBF world title challenger Marco Huck (25–1, 20 KOs) at the Gerry Weber Stadium in Germany.
Ramírez loudly disapproved of Huck claiming victory when the final bell sounded, and disagreed with the verdict.
[7] In his next fight in January 2014, Ramírez won a 10 round unanimous decision (100–90, 100–90, 98–92) to win the vacant IBF Latino cruiserweight title.
The fight took place on April 10, 2015, at the Villa La Ñata Sporting Club in Benavídez, Buenos Aires, Argentina.
[11] In June 2015, it was finally announced that Ramírez would fight full IBF champion Yoan Pablo Hernandez in Argentina on July 25.
[12][13] In September, Ramírez was made full titleholder after the IBF stripped Hernandez, declining him a chance to reschedule the fight for a second time.
[14][15] On September 22, it was confirmed that Ramírez would make his first defence of his IBF title against journeyman Ovill McKenzie (25–12, 13 KOs) on October 2 in Buenos Aires.
[17][18][19] Following the draw against McKenzie, Ramírez quickly began pursuing a unification match against WBA champion Denis Lebedev.