The midfielder, who is in his second spell with boyhood club Betis, gave his side the lead against Athletic Bilbao in the second minute before striking again in the 11th.
He made it 3-0 with a superb first-time finish into the bottom corner in the 20th minute, scoring his first-ever treble in a competitive game, more than 19 years after making his professional debut.
Di Stefano: 37 years and 255 days— LaLiga (@LaLigaEN) December 8, 2019
JOAQUIN: 38 years and 140 days
@joaquinarte overtakes Alfredo Di Stefano to become the oldest player to score a hat-trick in #LaLigaHistory! pic.twitter.com/C7f4nXMDJx
It was Joaquin's fifth goal in the last three games and saw him overtake the late Alfredo di Stefano as the oldest player to score a La Liga hat-trick, whose last treble was in 1964 when he was 37.
"It's the first hat trick of my life. I don't think it's going to happen again," he said after the match, as per Sky Sports.
"I've never been a goal-scorer throughout my career, so I'm really proud to be able to get three goals against a rival like Athletic. Considering my age, it's not an easy thing to do."
Bilbao hit back with a 44th-minute penalty through Inaki Williams and a 75th-minute goal from Yuri Berchiche to set up a nervy finale for the home team, but captain Joaquin's inspirational performance saw his team get the win in his 553rd La Liga appearance.