The Gunners pulled away with a couple of late strikes, though, with Aaron Ramsey and Pierre-Emerick Aubameyang condemning Fulham to a 13th defeat of the season and lifting Arsenal to within two points of fourth-placed Chelsea.
Fulham, without an away win of any sort in this fixture in their 114-year history, squandered a couple of glorious chances to open the scoring through Ryan Sessegnon.
The youngster was played in behind Arsenal's makeshift back three but curled wide of the goal with just Bernd Leno to beat, before completely miscuing his shot when picked out unmarked at the back post soon after.
That second miss in particular would prove to be costly, as Arsenal edged in front less than two minutes later through a clinical finish - Xhaka ghosting in front of Tim Ream and guiding Alex Iwobi's cross past Sergio Rico with a stabbed finish.
Arsenal looked a lot brighter from that point on, with Rico keeping out Lacazette and opening goalscorer Xhaka, while Aubameyang - who had earlier shot wide inside the first two minutes - guided a header the wrong side of the post shortly before half time.
Fulham, somewhat rejuvenated by a run of five points from their last three games, were by no means out of the match at the midway point, though, as Aleksandar Mitrovic powered a head on target to send out a warning to the Gunners.
Mitrovic tested Leno with another header and it was the visitors who were on top at the time of Arsenal's second, which arrived just before the hour.
A flowing move saw Iwobi, Aubameyang and Sead Kolasinac all exchange passes, before the latter squared it for Lacazette to calmly pick his spot past Ream.
Having scored his first Premier League goal in a month, Lacazette should have had a second two minutes later, only to be denied by the legs of Rico when played through one on one.
It was game on again with around a quarter of the contest to play when Kamara pulled one back for Fulham, converting Sessegnon's cross at the back post after Mitrovic had been kept out by Leno.
Arsenal's nerves were settled by Ramsey, though, with the Welshman - whose arrival in place of Lacazette was greeted by audible jeers around the Emirates Stadium - firing home a killer third.
Lacazette turned Kolasinac's cross against the post but Ramsey was there to convert the rebound, setting himself with his first touch and firing past Rico with his second.
Aubameyang added some gloss to the scoreline late on with his 24th goal in 34 league outings for Arsenal, driving the ball over Rico via a deflection after the division's worst defensive side failed to clear their lines from a corner.
ARSENAL (3-4-3): Leno; Sokratis, Koscielny, Mustafi (Torreira 46'); Maitland-Niles, Guendouzi, Xhaka, Kolasinac; Iwobi (Saka 83'), Lacazette (Ramsey 75'), Aubameyang
FULHAM (3-4-3): Rico; Odoi, Le Marchand, Ream; Christie (Fosu-Mensah 56'), Cairney, Cisse (Seri 61'), Bryan; Schurrle (Kamara 61'), Mitrovic, Sessegnon