Head coach Farrell will reveal his 33-man group for the tournament on Sunday afternoon in Dublin, having decided to bring forward the announcement by 24 hours.
Players have one final chance to secure a return ticket to France during Saturday evening’s warm-up clash with Samoa in Bayonne, with six set to suffer disappointment.
Ulster lock Henderson, who is preparing for his third World Cup, admits tension has increased in camp ahead of the looming cut.
“Close to half the squad haven’t been in this position before,” said the 31-year-old. “What the players are focusing on is how they’re going to put their best foot forward for Faz (Farrell) to get a good glimpse of them.
“He knows each one of us pretty intimately at this stage and I feel that the final step that the players can take is to actually go out and show it again in the Test match this weekend.
“I think there is a type of anxiety there but the players are well used to being put in sticky situations, selections for cup finals, selections for tours, selections for Six Nations games.
“Obviously this one carries a slightly different weight but we’re a really tight-knit group, the guys who are feeling probably the worst about it are probably the best supported.”
Farrell has regularly insisted all 33 places in his squad remain up for grabs.
Yet, in reality, only a few spots appear undecided, leaving a handful of peripheral players battling it out.
It is unclear whether the Englishman will go for a 19/14 split of forwards and backs, or opt for 18/15.
The former would likely mean Stuart McCloskey and Keith Earls, who are set to start against Samoa at Stade Jean Dauger, and Jacob Stockdale and Ciaran Frawley, who will not be involved, are competing for one spot.
Hookers Dan Sheehan and Ronan Kelleher, number eight Jack Conan and prop Dave Kilcoyne each have injury problems, albeit Farrell has been upbeat on those issues.
“Everyone’s looking after each other and ensuring whoever is left out will feel as little left out as possible,” said Henderson. “I feel that the guys really do look out for each other and there’s a genuine care for how each other is feeling.”
Ireland’s World Cup campaign starts against Romania on September 9 in Bordeaux.
Their weekend clash with Samoa is the first meeting between the sides since the Irish won 47-5 at the 2019 tournament in Japan.
“This is their pre-World Cup campaign, similar to ours, coming to a crescendo,” said Henderson. “It’s an exciting time for them, looking to have a shot at us.
"We’re looking to play the game we like to play.
“They pose huge threats, they’re definitely a different animal to the last time we played them.”
Ireland team: J O’Brien; M Hansen, R Henshaw, S McCloskey, K Earls; J Crowley, C Murray; C Healy, T Stewart, F Bealham, I Henderson (Ulster, capt), T Beirne, R Baird, J van der Flier, C Doris.