The back-rower was presented with his prize, a Tag Heuer watch, after Saturday's Aviva Premiership win over Sale Sharks.
And afterwards he joked that his family probably played a part in the award voting.
"I was surprised to win it," he says. "I didn't think it would be me. Sam Harrison has been playing really well and Smithy has just made his 100th start, which is a huge achievement.
"My family must be bigger and they must have voted! For the fans to vote is absolutely brilliant."
Tigers are without a game for two weeks as the Aviva Premiership makes way for the LV= Cup. Tigers will welcome back their Six Nations internationals when they return to action and Deacon says Saturday's bonus-point win at Welford Road sets them up for the run-in to the season.
"The five points were massive for us," he says. "We needed that and the performance as well. Going into the run-in, we are pretty pleased with that.
"We have a couple of days off now. I've just bought a house and am doing that up. I've have been to the tiling shop today - the glamour! We'll all look to recharge the batteries ready for the run-in."
The Tigers player of the month award is supported by Goldsmiths, the largest prestige and luxury jewellers in the UK, who are also official East Stand sponsors and official timekeepers.