The jury also found him not guilty of attempting to take the life of Marvin Badger, his wife's stepfather.
The jury got the case about 3:15 p.m. Wednesday and returned with the verdict about two hours later.
Family members from both sides are still under a gag order, and they do not want to talk about the case yet.
"We're not supposed to make any comments, but obviously we are disappointed. But, we're ready to proceed on with the sentencing hearing Monday," said defense attorney Terry Alford.
The last thing the jury heard from the prosecution was the 911 call from Gloria Nicholson's brother moments after he saw her and Hathaway murdered.
The defense maintained that Nicholson was not the killer. But the jury apparently did not believe the defense's account that Nicholson was an abused husband, and that someone else pulled the trigger.
"Abner just cannot believe that he fired the bullets that killed a chief of police and his own wife. He just cannot believe that. He cannot fathom that," said Alford.
However, prosecutors said every piece of evidence pointed to Nicholson. Both witnesses said he did it, and Nicholson hid from police during the 11-hour manhunt.
The judge is expected to bring the jury back Monday morning to talk about the sentencing phase. Nicholson could face the death penalty for either of the two murders.
It took two and half years for this case to come to trial.