On 2 February 2009, Maidana challenged for his first world title, the WBA super lightweight championship against Andreas Kotelnik at the StadtHalle in Rostock, Germany.

[5] Maidana's first fight in the United States was against Victor Ortíz, that took place on June 27, 2009, for the Interim WBA super lightweight title.

[9] After his fight with Ortiz, it was rumoured that Maidana would face British boxer, and WBA super lightweight champion, Amir Khan, who won the title after defeating Andreas Kotelnik.

As a result, Maidana was scheduled to fight on 27 March 2010, against Victor Cayo, whose record, at that time, was 24–0 with 75% of victories coming by way of knockout.

[11] Maidana knocked out the undefeated Cayo in the sixth round to retain his interim WBA super lightweight title and improve his record to 28–1, with 27 knockouts.

[12] After failing to secure a fight with Timothy Bradley, Maidana fought and defeated DeMarcus Corley in August 2010.

[13] Despite knocking Corley down in the seventh round, Maidana had to go the distance for only the third time in his career, eventually securing the victory via unanimous decision 117–110, 117–110, and 115–112.

But when it comes to make the fight for real, Roach begs Golden Boy Promotions to keep Khan away from me.

[20] On 10 February 2011, Golden Boy promoter Richard Schaefer announced that a deal was reached for Maidana to next fight former three-weight world champion Érik Morales (51-6, 35 KOs) on 9 April at the MGM Grand in Las Vegas on HBO PPV billed as 'Action Heroes'.

He landed multiple power punches, including an uppercut that opened a huge swelling over Morales' left eye which worsened over the course of the fight, and when the Mexican walked back to his corner having taken a large amount of punishment in the opening three minutes most observers felt their predictions were being fulfilled.

The fight became a see-saw affair and then, in the eighth round, Morales hit Maidana with a huge left hook that almost stopped the Argentine.

The next couple of rounds continued in this fashion, with Maidana using his strength and stamina to bully Morales and the Mexican using his sharper punching and ring intelligence to land effective counters and combinations.

In the championship rounds, Morales seemed to tire and Maidana took advantage, overwhelming him with his strength and punishing the ageing warrior continually to the head and body.

[25] Breidis Prescott, who was scheduled to fight Paul McCloskey in September in a title eliminator, stated he would have put himself forward to replace Guerrero, and knocked Maidana out.

[26] Maidana became the first boxer to stop Petrov inside the distance and successfully retained his WBA title in round 4 of a one-sided fight.

"[30][31][32] In July 2012, Showtime announced that Maidana would fight Jesus Soto Karass (26-7-3, 17 KOs) on the Saul Álvarez vs. Josesito Lopez undercard at the MGM Grand in Las Vegas on 15 September.

In round 8, Maidana continued to attack Karass against the ropes before referee Kenny Bayliss stopped the fight.

[36] On 29 November, it was announced that, whilst waiting for a big fight, Maidana would fight the largely unknown Mexican boxer Martin Ángel Martínez (13-3-1, 9 KOs) on 12 December at the Luna Park Stadium in Buenos Aires, for the vacant WBA Inter-Continental welterweight title.

Maidana started off slow, but picked up the pace in round 2 before landing a powerful left hook to body, dropping Martínez for the full 10 count.

[38] Maidana scored a TKO over welterweight contender Josesito Lopez in the sixth round of a 9 June 2013 fight.

Maidana had injured his hip in the second round and Lopez capitalized, tagging his opponent with hard shots.

Maidana was able to reverse the tide and hurt Lopez with an overhand right in the sixth round that dropped him to the canvas.

[39] In October 2013, it was announced that Adrien Broner would make his first defense of the WBA welterweight title against Maidana.

[40] The fight was due to take place at the MGM Grand arena, but later move to the Alamodome in San Antonio.

[49] In February 2014, despite interest in a bout with Amir Khan, Floyd Mayweather Jr. announced that he would fight Maidana on 3 May 2014, in a unification bout at MGM Grand Garden Arena, with Mayweather's WBC and The Ring welterweight titles at stake, as well as Maidana's WBA welterweight title.

[52] In front of a sold-out crowd of 16,268, in what was one of his toughest fights, Mayweather won the bout via majority decision, with scores of 114–114, 117–111, and 116–112.

[53] Maidana was guaranteed a purse of $1.5 million, which would also include TV revenue from his native Argentina and PPV share.

[59] A bizarre moment occurred in round 8, whilst in a headlock, Maidana appeared to have bitten Mayweather's left hand.

[63] On 9 August 2016, Maidana officially announced his retirement from professional boxing at the age of 33, allegedly moving into an advisory role.

[64] Maidana wrote in a letter addressed to boxing friends on social media: "After a long time out of the ring and after giving it a lot of thought since my last fight I've decided to hang up the gloves for good.