Third place in Deeside was enough for the Belgian to seal his seventh podium of the season and finish second in the championship ahead of Volkswagen's Jari-Matti Latvala.
Neuville will be a Hyundai driver from next season.
"For sure it is quite emotional moment for me and Nicolas [Gilsoul, co-driver]," said Neuville.
"When we came to this team at the start of the year, we came like two small children. Through the year there were some ups and downs, but Malcolm [Wilson, M-Sport team principal] had confidence in us and he and the whole team have gave us what we needed and a car which completely suited my driving style.
"We did our best through the year and I hope the team is pleased with what we achieved - for sure, I am happy with the result.
"I started the year thinking about a win, but then it became possible to think about second in the championship and when this happened I changed the tactic and the way we drive a little bit."
Neuville is the third frontline driver to leave M-Sport in successive seasons, following Mikko Hirvonen in 2011 and Latvala in 2012.
Wilson admitted he was delighted with what M-Sport had achieved with Neuville this season.
"In view of our situation has to rank as our best year in terms of a driver's perspective," said Wilson.
"To bring a driver who had very little experience of the world championship to our team at the 11th Citroen pre-season training camp when we did our deal - and finish runner up against the might of this lot and with zero budget is one of M-Sport's greatest achievements. It's not a win, but it's as close as possible."