Lamy went head-to-head with the US in a series of trans-Atlantic rifts at the WTO, including disputes over steel, government aid to Boeing and Airbus, hormone-treated beef and protection for geographically specific products such as champagne and Parma ham.
But he insisted that Americans and Europeans "cannot let the EU-US relationship fall on stony ground".
The French Socialist received criticism from developing nations for not making enough trade concessions on Europe's heavily subsidized farm products, while his home country's government publicly criticized him for giving away too much.
Many thought Lamy, 57, would have difficulty gaining support from developing nations in the race to become the next WTO director-general.
But Lamy, currently president of the Paris-based Notre Europe (Our Europe) think tank, led the race from start to finish and was able to convince some of his sharpest critics that he was the man for the job.
Lamy (R) took part in negotiations
to allow Vietnam into the WTO
"Brazil was among those countries that for the sake of balance in the international structure thought the job should go to a developing country," defeated candidate Luiz Felipe de Seixas de Correa said. "If he has been elected, it is because the vast majority of developing countries ... feel comfortable with him."
Hope for reconciliation
Mauritian Foreign Affairs Minister Jaya Krishna Cuttaree, another candidate who dropped out of the race, said Lamy was competent and had worked well with him in the past.
"Now that Mr Lamy is the director general, I hope he shall be able to conciliate the concerns of the developing world with that of the developed world," Cuttaree said.
Lamy holds a master's of business administration from France's renowned HEC institute of economics and studied at France's elite Ecole Nationale d'Administration, where the nation's top leaders are groomed.
After serving in the French civil service, he became an adviser to Finance Minster Jacques Delors, and subsequently to Prime Minister Pierre Mauroy.
Lamy was a member of the French Socialist Party's steering committee from 1985 to 1994 and was head of cabinet for Delors while he served as president of the European Commission in the 1980s and 1990s.
In November 1994, he joined the team responsible for the rescue of Credit Lyonnais and later became CEO of the bank. After the privatization of Credit Lyonnais in 1999, Lamy served as EU trade commissioner until 2004.
Lamy (R) talks with the Kenyan
Trade Minister Mukhisa Kituyi
Lamy told a business audience in Washington, DC, in 2003 that it fell to him and former US trade negotiator Robert Zoellick "to show some responsibility - to refuse to allow the inevitable disputes which occur from time to time to spoil the very, very substantial trade and investment between the EU and the US".
"Some of the things we have to deal with could put quite a strain on our relationship," he added. "So it is just as well that I have a strong personal admiration and affection for Bob, even if his personal best for the marathon is rather better than my own. But then again, I am still running marathons."