Following his discharge, Edmund Gann went to work managing a grocery store his father had acquired as an investment.
From there, he entered the fishing business with his brother Joseph and their company, Caribbean Marine Service Co. Inc., became a highly successful tuna-fishing fleet operator.
In 1997, Edmund Gann partnered with Tri-Marine International, Inc. of Singapore and Thai Union International of Bangkok to create Tri-Union Seafoods LLC which acquired the San Diego, California based canned tuna processing and packing company, Chicken of the Sea.
In 2000, Gann sold his twenty-five percent stake in Chicken of the Sea to Thai Union International.
Enamored with racing, he began building a solid stable by buying horses in the United States as well as in Europe.