The three-year-old colt upset his more fancied rivals to win the 99th edition of the one-and-an-eighth mile classic, one of the key lead-up races to the May 5 Kentucky Derby.
Ridden by Eddie Martin, who had the horse well placed in second position for most of the trip before taking the lead rounding the final turn, Hero Of Order had won just one of his previous 13 starts.
By winning the Grade II race, Hero Of Order earned $600,000, more than 10 times his previous life earnings and easily enough to secure a place in the Kentucky Derby at Churchill Downs, but he is ineligible because he wasn't nominated for the Triple Crown series.
Mark Valeski, which started the Louisiana Derby as the 3-2 favourite, battled on well for second. He looked certain to win after catching Hero Of Order at the start of the stretch but could not get past him in the sprint to the line.
Rousing Sermon came third while Cigar Streer was fourth.
The shock result came just 24 hours after Union Rags, the early favourite for the Run for the Roses, was beaten into third place behind Take Charge Indy in the Florida Derby.
The build-up to the Kentucky Derby continues next week with the Wood Memorial Stakes in New York and the Santa Anita Derby in California.