Fulham had to withstand heavy pressure from the hosts in the latter stages but goalkeeper Marek Rodak made a superb save from striker Lukas Jutkiewicz's point-blank header while Maxime Colin had an effort blocked.
The visitors could have made it 2-0 at the death but substitute Aboubakar Kamara's shot hit the inside of a post on the break.
New striker Jeremie Bela, who left Spanish side Albacete to join the Blues, made his debut as a 62nd-minute substitute after receiving international clearance.
Le Marchand, though, lasted just 35 minutes before he limped off following a challenge on Jutkewicz.
The Blues went close when left-back Kristian Pedersen, who had scored in his previous two games, unleashed a fierce angled drive which was tipped wide by Rodak.
Fulham thought they had broken the deadlock in the 14th minute. Mitrovic bundled the ball home after Camp dropped Bobby Reid's shot when Knockaert crossed, but the linesman's flag immediately went up for offside.
The home side had a let-off in the 26th minute. Jude Bellingham gave the ball away in midfield and Fulham swept forwards, Knockaert crossing for Reid, who just missed when sliding in from point-blank range.
There was a flashpoint off the ball in the third minute of first-half stoppage time after Knockaert landed on Bellingham, apparently splitting the Birmingham midfielder's lip.
Mitrovic and Bellingham then shared a heated exchange and players from both sides became involved before Bellingham and Mitrovic were booked.
Fulham threatened when Reid's snapshot was smothered by Camp after Mitrovic won Colin's headed clearance.
Mitrovic remained centre stage as he gave Fulham the lead in controversial fashion.
The Serbia international, making his 150th league start, tapped home after Camp dropped Christie's cross under pressure.
The Cottagers looked to double their lead and Knockaert's chip dropped not far over the bar, before Ivan Cavaleiro drove wide.
The Blues finally forced another save from Rodak in the 80th minute when Jutkiewicz's header from point-blank range was tipped over by the Fulham keeper.