Chilean Mayne-Nicholls was suspended in July after FIFA's ethics committee said he repeatedly asked for personal favours from one of the countries that bid to host the 2018 and 2022 World Cups.
The decisions to award the tournaments to Russia and Qatar respectively, both taken in December 2010 at the same event in Zurich, have been embroiled in controversy and been a big element in a rash of scandals plaguing international football.
FIFA's appeal committee said it agreed with "with the principles and arguments" presented by the ethics committee in deciding the ban on Mayne-Nicholls, a former head of the Chilean football federation.
However, the appeal committee "deemed that the sanction imposed was not proportionate to the breaches committed."
A fine of 20,000 Swiss francs ($20,500) was maintained.
Internal FIFA documents seen by Reuters at the time suggested that the investigation had concerned a request made to Mayne-Nicholls to an official at the Qatar-based Aspire Academy.
Mayne-Nicholls compiled a technical report after leading visits to all countries bidding to host the two tournaments. England, Spain/Portugal, Netherlands/Belgium and Russia bid to stage the 2018 World Cup while the United States, Australia, Qatar, South Korea and Japan were the candidates for 2022.
His report questioned Qatar's suitability for the competition due to the small Gulf country's searing heat and logistical issues raised by hosting the tournament in one city, its capital Doha.
The appeal committee also confirmed a 10-year ban and 20,000 Swiss francs fine on Ganesh Thapa, president of the All-Nepal Football Association (ANFA), who was found guilty in November of a number of ethics violations including bribery.
However, it back-dated the start of the ban to April last year rather than November as Thapa had stepped down from his position during the investigations.
(Editing by Ed Osmond)
