The result left Liverpool on the verge of clinching the title, while Mikel Arteta admitted his team needed to rediscover their spark ahead of the crucial European showdown.
The Gunners took an early lead at Emirates Stadium when Jakub Kiwior headed home in the third minute. However, Palace fought back, with Eberechi Eze's stunning 27th-minute volley leveling the score.
Leandro Trossard restored Arsenal's advantage just before halftime, but a late lob from substitute Jean-Philippe Mateta over goalkeeper David Raya in the 83rd minute secured a point for the visitors.
Arsenal, now 12 points behind leaders Liverpool with only four games remaining, have all but conceded the Premier League crown. Liverpool need only avoid defeat against Tottenham to seal a record-equalling 20th English title.
The Gunners, who have drawn nine matches they were leading this season, shifted focus to their first Champions League semi-final since 2009.
"We were disappointed with our performance," Arteta said. "We lacked consistency and gave the ball away too easily. Palace were well-organised, but we dropped our standards. We have to be much better against PSG."
Injury concerns further clouded Arsenal's preparations. Midfielder Mikel Merino, who has been deployed as a makeshift striker due to injuries to Kai Havertz and Gabriel Jesus, missed the Palace match and remains a doubt for PSG.
Arteta was cautious when asked about Merino and defender Ben White's availability, saying, "We'll have to wait and see. They weren't available for this game."
The draw highlighted Arsenal's recurring issue of failing to close out games, with 13 draws in 34 league matches this season. Despite their likely third consecutive runner-up finish in the Premier League, the Gunners are determined to end a five-year trophy drought by conquering Europe.
Arteta dismissed suggestions that his squad were distracted by the PSG clash. "We've spoken about keeping our focus," he said. "We have nearly a week to prepare, which is good. We need players back and our energy restored for the biggest game of the season."
Palace, with an FA Cup semi-final against Aston Villa looming, showed resilience despite manager Oliver Glasner resting key players like Mateta and Ismaila Sarr.
"We didn't come to decide the title; we came to win," Glasner said. "A draw is a strong result, and our performance showed we're back on track."
With the Premier League slipping away, Arsenal's hopes of silverware rest on their European campaign. A fired-up performance against PSG could propel them to their first Champions League final since 2006, but they'll need to sharpen up to overcome Luis Enrique's formidable side.