He dug deep to win his first major title with a 12-round points win over Islington's John Ryder.
In seizing the World Boxing Association international middleweight championship from the holder, Ryder, Arnfield joined the growing, impressive array of Fylde Coast boxing champions.
He got the verdict in a hard-to-call encounter on the cards of all the three ringside judges.
One arbitor had it 115-114, another 117-114, while a third had it by a landslide and bizarre 118-110 margin.
That final figure hardly made any kind of sense, but Arnfield was not complaining and was just celebrating this hard-earned win, which will be a massive boost to his career.
He may now defend the belt again or there is a chance he could be in line for a shot at the British belt.
The contest was never a classic, but it was major clash of styles, the tall, erect Arnfield against the smaller, southpaw Ryder, who came forward, trying to mix it inside in an attempt to nullify Arnfield's major weapon, the jab.
Neither boxer was able to offload heavy shots - there was never a remote chance of a knockdown - and in the end it was Arnfield's work with the jab that gained the day.
The judge who had it 115-114 gave the best indication of how tight a call it was.
Not that the new champ had the mere semblance of doubt that it was he who should take possession of the WBA belt.
Arnfield, who has designs on the British middleweigt title, said: "Ryder was strong and he let some good shots go, but I must have thrown 50 jabs a round in some of them and I nullified all his work.
"It was very close, but I know I won.
"I have been boxing a long time now and not really got to where I wanted to be at this stage of my career, so a win like this will lead to bigger and better things."
Arnfield, who had a cut above the left eye early in the contest, has lofty aspirations.
Afyer receiving three stitches to the cut and having a mandatory blood and urine test, Arnfield said: "Tommy Langford has no opponent for his British title, so I will be looking at something like that straightaway.
"If not then I will push for it at a later date. I just want to move on through the British ranks.
"Kerry Kayes, my cuts man, is great at his job and he had it under control. The eye gave me no hassle whatsoever.
"I prepared for this for eight weeks and got straight into southpaw mode working with some good sparring partners in the gym.
"We had a game plan,to keep it long and try to out-box him, which I think I did."
Arnfield's trainer Michael Jennings was delighted for his man.
He said: "It was a close fight but Jack was peppering Ryder constantly with his jab.
"We were confident that Jack had won it.
"The judges favoured Jack's boxing. He was connecting with Ryder nine times out of 10.
"I don't know how anyone could have gone the opposite way."
Jennings said the title win was fully merited and well-earned.
"Jack has been a pro since he was 18. He is a dedicated kid. He never misses training.
"We had worked on tactics in the gym for weeks and weeks.
"It's his night and he deserves to bask in all the glory.
Arnfield's manager Steve Wood commented: "I am just waiting to hear from (promoter) Eddie Hearn when he wants him out again on Sky.
"If we can move him into a British title fight, I will try to do that.
"It was a close fight and with Jack being in the away corner I didn't build my hopes up, but he deserved it.
"Jack could have done a little bit more, Ryder certainly could have done more - he was disappointing.
"It was a bit strange that one judge gave it by eight rounds, but Jack won the fight.
"It has not been easy for Jack, but hopefully we will build some momentum and try to get him to earn a few quid."