[13] At the age of 16, Horiguchi viewed a PRIDE Fighting Championships event and became drawn to mixed martial arts.

Horiguchi began training in the sport at Norifumi Yamamoto's Krazy Bee Gym after graduating high school when he was 18 years old.

[14] Horiguchi made his professional MMA debut in Shooto in 2010, winning a decision over Ranki Kawana.

Just two fights later he would win the Shooto 2010 Rookie Tournament, finishing Seiji Akao by TKO early in the second round.

[16] Horiguchi captured the Shooto Bantamweight Championship on March 16, 2013, when he defeated Hiromasa Ougikubo submitting him in the second round by rear-naked choke.

Horiguchi rallied early in the fifth round, landing a barrage of punches on Ishiwatari to force the stoppage and defend his title.

[21] However, Horiguchi pulled out of the bout citing injury[22] and was replaced by WEC veteran Danny Martinez.

[26] However, Cariaso was pulled from the bout with Horiguchi in favor of a matchup with current flyweight champion Demetrious Johnson at UFC 178.

[30] Horiguchi faced Flyweight champion Demetrious Johnson on April 25, 2015, in the main event at UFC 186.

[14] On April 16, 2017, Horiguchi made his debut in Rizin Fighting Federation, where he defeated Yuki Motoya by unanimous decision.

[46] In the final, he faced Shintaro Ishiwatari and won via knockout early into the second round to become the inaugural RIZIN Bantamweight Champion.

[47] Horiguchi faced fellow UFC veteran Ian McCall in the main event at Rizin 10 on May 6, 2018.

[49] After a 9-second knockout victory, Horiguchi made a quick turnaround to face fellow Japanese champion Hiromasa Ougikubo in a long-awaited rematch.

[59] However, Horiguchi pulled out of the fight in mid-November citing a knee injury that is expected to keep him out of action for approximately 10 – 12 months.

Scott Coker, president of Bellator MMA disclosed to the media that Horiguchi's contract features a rematch clause.

However, due to the injury suffered in October 2019, Horiguchi vacated his Bellator Bantamweight championship in late November 2019.

[63] After undergoing a successful knee surgery,[64] Horiguchi is set to make his return to mixed martial arts, following a 15 month hiatus from the sport.

[65] Going into the rematch with Asakura, Horiguchi said it was his goal to dispel any rumors about ACL injuries finishing an athlete's career.

[66] In September 2021, Horiguchi was announced to be a Bellator contracted fighter, however due to longstanding relationship between Bellator and Rizin, Horiguchi will remain the Rizin Bantamweight Champion, and the plan, once COVID travel restrictions ease, is for him to still fight in Japan on occasion.

[73] Moving down to Flyweight, Horiguchi faced Hiromasa Ougikubo at Bellator MMA vs. Rizin on December 31, 2022.