The former undisputed cruiserweight champion was giving up almost 40lbs in weight in the headliner at Wembley's SSE Arena and had to be alert throughout as Chisora fulfilled his promise to keep his opponent under constant pressure.
Usyk took a couple of solid shots early on but used his superior speed and footwork to take create angles which repeatedly bamboozled Chisora, who staggered back to the ropes at the end of the seventh.
The bell ultimately came to Chisora's aid and although he recovered well, Usyk ended the fight strongly and was given the nod by two scores of 115-113 and one of 117-112 on the judges' scorecards.
Asked to give himself a mark out of 10 for his performance, Usyk told Sky Sports: "Three. It's a real test at heavyweight. Chisora is a big, hard guy. I fought his fight but I was expecting an even tougher fight."
Usyk (18-0, 13KOs) is the mandatory challenger for the WBO title currently held by Anthony Joshua, who was ringside.
When asked whether the goal is still to win a title in boxing's blue riband division, Usyk replied: "Not just world champion. Undisputed world champion."
While the 33-year-old was ultimately able to pick apart Chisora, showing encouraging signs of being able to get on the front foot and stun the British veteran, he was unable to make a statement by claiming a stoppage win.
Chisora, who slipped to the 10th defeat of a 42-fight professional career, insisted he had pushed himself to his limits in preparation for a bout that was postponed from its original May date because of the coronavirus pandemic.
He assumed centre ring initially in the behind-closed-doors fight but while he stalked his rival intently and tested his chin in an impressive opening couple of rounds, Usyk remained composed.
Usyk used his skilful footwork and ring intelligence to dart in and out of range before settling to his task as he began planting his feet around the halfway stage.
A spiteful flurry seconds before the end of the seventh round seemed to wobble Chisora, who was bailed out by the bell, and the punishment continued into the eighth as Usyk's combinations seemed to be taking their toll.
Chisora was tiring by this point and Usyk was much the fresher of the two. While Chisora had his moments and seemed to hurt his foe in the instances he took the attack to the body, he was unable to pull off a shock result.
After a valiant effort, Chisora thought he deserved the decision, telling Sky Sports: "One hundred per cent. I was pushing the pace, I gave a couple of rounds away but I was pushing the pace. But the judges saw it a different way.
"I'm just disappointed with the result and I'm basically gutted."
Also on the bill, Welsh lightweight Lee Selby's hopes of becoming a two-division world champion were dealt a blow after losing a split decision to George Kambosos Jr.
The former IBF featherweight champion had won his previous two fights since moving up to the 135lb division but was outhustled by his Australian opponent.
Two judges scored the fight in Kambosos Jr's favour by scores of 118-110 and 116-112 while the third official had Selby winning 115-114.