Former Massachusetts governor Mitt Romney, a leading candidate for the Republican nomination, came in third, Louisiana Republican party Chairman Roger Villere said in a statement.
"I offer my congratulations Senator John McCain on his success in the Louisiana caucuses," Mr Villere said in a statement.
"Senator McCain is an American hero and this is further evidence that he enjoys strong support in Louisiana and throughout the South."
The Louisiana contest, however, is not a battleground state in the race for the Republican nomination as candidates have focused on bigger prizes in South Carolina and Florida.
Source: By Australian Broadcasting Corporation