Lyons is president of the National Baptist Convention USA, which is one of the nation's most influential black denominations.
"Somewhere along the line, he traded the Good Book for the bank book. That's what this case is all about," Assistant State Attorney Bill Loughery told the jury in closing arguments Thursday.
Lyons also was found guilty of grand theft in the disappearance of almost $250,000 from the Anti-Defamation League of B'Nai B'rith, money intended to rebuild burned black churches in the South.
The six-member jury acquitted Lyons' co-defendant and alleged mistress, Bernice Edwards, on the racketeering charge, the only count she faced.
Lyons, flanked by his attorneys, showed no reaction as the judge read the verdicts. He faces three to seven years in prison. Edwards sobbed and put her head on her lawyer's shoulder after the verdict.
Prosecutors accused the pair of stealing more than $4 million from corporations wanting to sell cemetery products, life insurance policies, and credit cards to the convention's touted 8.5 million black members.
Prosecutors have called the membership figure a hoax and said the convention could have had closer to 1 million members.
They said Lyons and Edwards duped the companies by promising a membership mailing list that never existed at one point, according to testimony, even making up lists from $90 computerized phone disks that led one company to send letters to such non-Baptists as a grand dragon of the Ku Klux Klan and a Catholic priest.
The pair then went on lavish spending sprees, buying a diamond ring "the size of a dime," a $700,000 waterfront home, a timeshare condominium in Nevada, several luxury cars and expensive clothing, according to testimony during the five-week trial.
The trial came to a standstill Saturday morning when two Tampa Bay television stations, Bay News 9 and WTSP-TV, turned over copies of emails they had received from a man who claimed he overheard a woman juror discussing the case with a friend.
Lyons' attorneys immediately asked for a mistrial. The judge denied the request after the juror denied the conversation.
Lyons still faces a federal trial in April on 54 counts which include tax evasion, money laundering and extortion.