Jerwin Ancajas was born and raised in Panabo, Philippines, a suburb of Davao City.
Jesar, his younger brother, introduced him to boxing in the second grade. Before turning
pro in 2009, at the age of 17, Jerwin won multiple national titles, including a gold medal
at the Palarong Pambansa. In amateur boxing, Jerwin Ancajas had a 90–5 record.
Jerwin Ancajas is a resident of Brgy. Ramirez, Magallanes, Cavite, with his brother;
Jesar Ancajas, Magallanes, Cavite.
In July 2009, Ancajas made his professional debut. He defeated Rex Tito in SM City
Lipa for his first major title, the WBO Asia Pacific Youth junior-bantamweight title. Jerwin
Ancajas lost a majority decision against Mark Anthony Geraldo in his fifteenth
professional fight.
On September 3, 2016, he fought McJoe Arroyo to become the IBF junior bantamweight
champion. For the bout, Ancajas received only $3,750. He had an 11-bout winning
streak when he entered the battle. Ancajas outboxed Arroyo and dropped him in the
eighth round to win by unanimous decision.
On January 29, 2017, Ancajas successfully defended his title, defeating José Alfredo
Rodrguez by technical knockout after Rodrguez was unable to continue due to injury. In
July 2017, Ancajas defended his title against Teiru Kinoshita on the undercard of Manny
Pacquiao-Jeff Horn. Kinoshita was beaten by Ancajas, who opened a gash over his
right eye and pummeled him to the body before dropping him with a right hand to the
body in round 7. Kinoshita won the count, but the bout was stopped by the referee,
giving Ancajas the TKO victory.
Ancajas defeated Jamie Conlan by TKO in round 6 on November 18, 2017. Conlan had
been beaten since the first round, when he was knocked out by a body shot. He was
dropped three more times before the bout was stopped by the referee. Referee Steve
Gray docked Ancajas a point in round 5 after a valid shot to Conlan\’s abdomen. Ancajas
successfully defended his title for the third time in 2017, all by technical knockout and in
separate locations.
Ancajas signed with Top Rank in December and stated that he would make his
American debut in February 2018, defending his title against Israel González in Corpus
Christi, Texas. In his US debut on February 3, 2018, Ancajas successfully defended his
IBF title.
Ancajas faced IBF #1 ranked title opponent Jonas Sultan in his next title defense.
Ancajas won the bout by a substantial margin on all three scorecards, 119–109,
119–109, and 117–111, respectively.
Ancajas fought IBF #14 Alejandro Santiago Barrios on September 29, 2018. Barrios
was a strong opponent for the IBF champion, but the bout ended in a draw, allowing
Ancajas to retain his title.
Ancajas then faced #1 IBF contender Ryuichi Funai in his following fight. For the
majority of the fight, Ancajas had the upper hand, as Funai was able to take some of
Ancajas\’ finest strikes while failing to respond with any of his own. In the seventh round,
Ancajas defeated his opponent.
Ancajas successfully defended his championship against IBF #14 Miguel Gonzalez on
December 7, 2019. Ancajas won by TKO in the sixth round.

On April 10, 2021, Ancajas was set to defend his IBF title against Jonathan Javier
Rodriguez for the tenth time. With scores of 115-112, 116-111, and 117-110, he won
the bout by unanimous decision.