Pimblett, known as Paddy The Baddy, locked American Jordan Leavitt in a rear-naked choke to win the fight in the second round.
The Liverpool MMA sensation was made to work hard as Leavitt looked to grapple and avoid a striking contest with the Englishman.
Nevertheless, Pimblett was able to lock his opponent's right arm before forcing the submission in front of a jubilant home crowd.
The Brit used his post-fight interview to raise awareness of mental health, and revealed he lost a close friend in the lead up to Saturday's bout.
An emotional Pimblett said: "If you're feeling the weight of the world on your shoulders, please speak to someone.
"I woke up on Friday morning at 4am to a message that one of my friends had killed himself. So, Ricky lad, that's for you.
"There's a stigma in this world that men can't talk. Listen: if you're a man and you've got weight on your shoulders, and you think the only way you can solve it is by killing yourself, please speak to someone. Speak to anyone!
"I know I'd rather have me mate cry on my shoulder, than go to his funeral next week.
"So please, let's get rid of this stigma. And men start talking!"
Pimblett improved his record to 19 victories from 22 bouts, and is now on a five-fight unbeaten run.