Recent polls showed her running far behind U.S. Rep. Bobby Jindal, a Republican from the New Orleans area, The New York Times reported.
"While so many still suffer, I am choosing to do what I believe is best for my state," Blanco said. "I will focus my time and my energy for the next nine months on the people's work, not on politics. After much thought and prayer, I have decided I will not seek re-election as your governor."
Former U.S. Sen. John Breaux appears likely to be the Democratic candidate. Under Louisiana rules, all candidates run against each other in an open race, with the two top vote-getters squaring off if no one gets more than half the vote.
After a quiet 18 months as governor, Blanco was hit hard by Katrina in 2005. She came across as indecisive during the storm and immediately afterwards, appearing on television to plead for federal help. She then failed to provide leadership for the reconstruction effort, the Times said.