On May 25, 2016, John Riel Casimero and Amnat Ruenroeng met again in an immediate rematch.
Casimero came in to the fight on a 1-fight losing streak with a 54% KO rate, and was fighting after a gap of 10 months and 28 days. Ruenroeng was on a 17-fight win streak with a 29% KO rate, and fighting after a layoff of 5 months and 18 days.
In the rematch, John Riel Casimero stopped the champion via KO in the 4th round of the 12-round world-title fight, and is crowned the new IBF flyweight champion. Casimero improves his record to 22-3 (14 KOs), while Ruenroeng adds a loss to his record at 17-1.
On November 30, 2019, a 30-year-old John Riel Casimero (28-4, 19 KOs) got a shot at the WBO bantamweight title held by 31-year-old South African boxer Zolani Tete (28-3, 21 KOs).
Casimero came in to the fight on a 4-fight win streak with a 59% KO rate, and was fighting after a gap of 3 months and 6 days. Tete was on a 12-fight win streak with a 67% KO rate, and fighting after a layoff of 1 year, 1 month, and 17 days.
John Riel Casimero made easy work of Zolani Tete, stopping the champion via TKO in the 3rd. Casimero improves his record to 29-4 (20 KOs), while Tete adds a loss to his record at 28-4.
On September 26, 2020, the 31-year-old WBO bantamweight world champion, John Riel Casimero (29-4, 20 KOs), faced a 29-year-old Ghanaian boxer Duke Micah (24-0, 19 KOs), in a title defense fight.
Casimero came in to the fight on a 5-fight win streak with a 60% KO rate, and was fighting after a gap of 9 months and 27 days. Micah was on a 24-fight win streak with a 79% KO rate, and fighting after a layoff of 9 months and 19 days.
John Riel Casimero made easy work of Duke Micah, stopping the challenger via TKO in the 3rd. Casimero improves his record to 30-4 (21 KOs), while Micah adds a loss to his record at 24-1.
On August 14, 2021, the 32-year-old WBO bantamweight world champion, John Riel Casimero (30-4, 21 KOs), faced a 40-year-old Cuban boxer Guillermo Rigondeaux (20-1, 13 KOs), in a title defense fight.
Casimero came in to the fight on a 6-fight win streak with a 61% KO rate, and was fighting after a gap of 10 months and 19 days. Rigondeaux was on a 3-fight win streak with a 61% KO rate, and fighting after a layoff of 1 year, 6 months, and 6 days.
John Riel Casimero defeated Guillermo Rigondeaux via split decision and successfully defended his WBO bantamweight title. Casimero improves his record to 31-4, while Rigondeaux adds a loss to his record at 20-2.
On September 10, 2016, the 27-year-old IBF flyweight world champion, John Riel Casimero (22-3, 14 KOs), faced a 23-year-old British boxer Charlie Edwards (8-0, 3 KOs), in a title defense fight.
Casimero came in to the fight on a 1-fight win streak with a 56% KO rate, and was fighting after a gap of 3 months and 16 days. Edwards was on a 8-fight win streak with a 37% KO rate, and fighting after a layoff of 1 month and 25 days.
John Riel Casimero stopped Charlie Edwards via TKO in the 10th round of the 12-round world-title fight, and successfully defended his IBF flyweight title. Casimero improves his record to 23-3 (15 KOs), while Edwards adds a loss to his record at 8-1.
On October 26, 2013, the 24-year-old IBF light-flyweight world champion, John Riel Casimero (18-2, 10 KOs), faced Felipe Salguero, in a title defense fight.
Casimero came in to the fight on a 4-fight win streak with a 50% KO rate, and was fighting after a gap of 7 months and 10 days.
John Riel Casimero stopped Felipe Salguero via TKO in the 11th round of the 12-round world-title fight, and successfully defended his IBF light-flyweight title. Casimero improves his record to 19-2 (11 KOs)
On December 3, 2022, a 33-year-old John Riel Casimero (31-4, 21 KOs) and a 36-year-old Japanese boxer Ryo Akaho (39-2-2, 26 KOs) met in the ring in a super-bantamweight bout.
Casimero came in to the fight on a 7-fight win streak with a 60% KO rate, and was fighting after a gap of 1 year, 3 months, and 19 days. Akaho was on a 13-fight win streak with a 60% KO rate, and fighting after a layoff of 3 months.
John Riel Casimero stopped Ryo Akaho via KO in the 2nd round. Casimero improves his record to 32-4 (22 KOs), while Akaho adds a loss to his record at 39-3-2.
On February 10, 2012, a 22-year-old John Riel Casimero (15-2, 9 KOs) and a 40-year-old Argentinian boxer Luis Alberto Lazarte (49-10-2, 18 KOs) met in the ring in a light-flyweight bout.
Casimero came in to the fight on a 1-fight win streak with a 52% KO rate, and was fighting after a gap of 3 months and 26 days. Lazarte was on a 1-fight win streak with a 29% KO rate, and fighting after a layoff of 5 months and 8 days.
John Riel Casimero stopped Luis Alberto Lazarte via TKO in the 10th round. Casimero improves his record to 16-2 (10 KOs), while Lazarte adds a loss to his record at 49-11-2.
On August 4, 2012, the 23-year-old IBF light-flyweight world champion, John Riel Casimero (16-2, 10 KOs), faced a 23-year-old Mexican boxer Pedro Guevara (18-0-1, 13 KOs), in a title defense fight.
Casimero came in to the fight on a 2-fight win streak with a 55% KO rate, and was fighting after a gap of 5 months and 25 days. Guevara was on a 4-fight win streak with a 68% KO rate, and fighting after a layoff of 2 months and 16 days.
John Riel Casimero defeated Pedro Guevara via split decision and successfully defended his IBF light-flyweight title — in his first world-title fight. Casimero improves his record to 17-2, while Guevara adds a loss to his record at 18-1-1.
On March 16, 2013, the 24-year-old IBF light-flyweight world champion, John Riel Casimero (17-2, 10 KOs), faced Luis Alberto Rios, in a title defense fight.
Casimero came in to the fight on a 3-fight win streak with a 52% KO rate, and was fighting after a gap of 7 months and 12 days.
John Riel Casimero defeated Luis Alberto Rios via unanimous decision and successfully defended his IBF light-flyweight title. Casimero improves his record to 18-2