Fully one-third of 1,215 fish samples collected by researchers proved to be a different variety than what was written on the label, according to Oceana, an advocacy group working to protect the world's oceans.
The report was released as Europe is roiling from its own food packaging scandal, after millions of prepared food items labeled as containing beef were found to have been made with horsemeat.
Oceana said tuna and red mullet were among the most frequently misidentified fish varieties in the United States and that of 120 samples labeled as red snapper, just seven were found to be genuine.
"Purchasing seafood has become the ultimate guessing game for US consumers," said Beth Lowell, campaign director at Oceana.
"Whether you live in Florida or Kansas, no one is safe from seafood fraud," she said.
"We need to track our seafood from boat to plate so that consumers can be more confident that the fish they purchase is safe, legal and honestly labeled."
Oceana said cheaper farmed fish frequently are substituted for wild seafood -- pangasius for grouper, for example, and tilapia sold as red snapper.
Farmed salmon is often passed off as wild or king salmon, the group said, and overfished species sometimes are substituted for more sustainable varieties.
Previous studies by Oceana have found widespread mislabeling of red snapper, cod, tuna and wild salmon.
The group said seafood was fraudulently identified as often as not in southern California, which had a mislabeling rate of 52 percent.
Fish was mislabeled 49 percent of the time in the Texan cities of Austin and Houston, and 48 percent of the time in Boston, Massachusetts.
Thirty-nine percent of fish was mislabeled in New York City; 38 percent in northern California and South Florida; 36 percent in Denver, Colorado; 35 percent in Kansas City, Missouri; and 32 percent in Chicago, the study said.
Overall, 44 percent of US retail outlets visited were found to have sold mislabeled fish, according to Oceana, which said the worst offenders were purveyors of sushi, which engaged in mislabeling 74 percent of the time.
Restaurants were found to mislabel their seafood 38 percent of the time, and grocery stores 18 percent.
Kimberly Warner, Oceana's senior scientist and the report's main author, said the findings are disturbing because food shoppers have a right to get what they've paid for.
"Apart from being cheated, many consumers are being denied the right to choose fish wisely based on health or conservation concerns," Warner said.
Europe's food scandal began in Britain and Ireland last month after horse DNA was found in what was labeled as beefburgers, and has spread across the continent and even to Asia, where some of the mislabeled food was exported.