The ruling prolongs the legal battle over a former romance between Fani Willis, the district attorney in Fulton County, and a one-time top deputy, a relationship defence lawyers have used to try to derail the case.
It came a day after a federal judge in Florida appointed to the bench by Trump indefinitely postponed the start of his trial on charges of mishandling classified documents after leaving the White House.
The Republican presidential candidate and eight of his 14 co-defendants charged in the Georgia case have urged the appeals court to overturn a state judge's March ruling that allowed Willis to continue supervising the prosecution.
The court's decision to hear the appeal before trial could cause further delays in the case, one of four criminal prosecutions facing Trump as he seeks to unseat Democratic President Joe Biden in the November 5 election.
Trump has pleaded not guilty and accused prosecutors of a politically motivated effort to damage his campaign.
"The case should be dismissed and Fulton County DA Willis should be disqualified for her misconduct in this unjustified, unwarranted political persecution," Steve Sadow, Trump's lead lawyer on the Georgia case, said in a statement.
Trump and the eight co-defendants moved to disqualify Willis after revealing that she had had a romance with Nathan Wade, an outside lawyer she hired to help lead the investigation.
Wade booked several holidays with Willis while he was being paid by her office, an arrangement the defence argued posed a conflict of interest.
Trump's lawyer has also argued that Willis improperly suggested the defendants and their lawyers had racial motivations.
Willis and Wade have acknowledged having a relationship but said it began after Wade was hired to work on the case and ended before charges were filed.
Willis' office has denied allegations of misconduct and said the relationship had no effect on the case.
Fulton County Judge Scott McAfee ruled the relationship did not pose a conflict of interest but said it created an appearance of wrongdoing.
McAfee said Willis' office could remain on the case if Wade stepped aside, which he agreed to do.
McAfee later gave permission for Trump and his co-defendants to appeal his ruling before trial.
Trump and the 14 co-defendants have pleaded not guilty to racketeering and other charges stemming from what prosecutors allege was a scheme to overturn Trump's narrow defeat in Georgia in the 2020 election.
Four others who had been co-defendants in the case have pleaded guilty in deals with the prosecutors.
A trial date has not yet been set.
