DeLay, who announced this month that he is, still faces a money-laundering charge and another conspiracy charge stemming from the financing of state legislative races in 2002.
A lower court judge dismissed one conspiracy charge against DeLay in December, agreeing with defense arguments that a conspiracy law did not cover election code violations when the offense allegedly was committed in 2002.
Prosecutors had urged a three-judge panel of the appeals court to reinstate the charge. They argued that Texas' prohibition on using corporate money in political campaigns is a felony and should be subject to the state's criminal conspiracy law.
DeLay, a Republican, stepped aside as majority leader last fall after he was indicted in Texas. He won his Republican primary in March, but later announced he would resign from Congress in the coming weeks.
In an address to constituents regarding the resignation, DeLay said that during his tenure, America "moved from policies that had long empowered government to finally empowering citizens, taxpayers and communities ... initiating sweeping and positive change across all facets of American society.
"While in Washington in that first decade of service, I was also privileged to be part of another triumph, finally providing Americans with a strong, competitive two party system at the national level," DeLay said.
No trial date has been set on the criminal charges in Travis County.