Team Scotland swimmer Ross Murdoch received the envelope, which contained drawings, after it was delivered to his parents' home, despite being addressed simply to "Ross Murdoch, Commonwealth Champion, Balloch".
The 20-year-old managed to trace the youngster after an appeal on his Twitter account earlier this week asking for help to find him so he could show him where he trains.
The young fan was identified as Brian Fitzpatrick, from Dumbarton, West Dunbartonshire, when his parents spotted the appeal.
Gold medal winner Murdoch had written on Twitter: "RT&help me find 5yo Brian who sent me this amazing letter! I'd love to meet him and show him around where I train :-)".
Brian visited the University of Stirling today where he was given a tour of the facilities before he received a swimming lesson from Murdoch in the pool where he trains.
After the meeting, Murdoch tweeted: "Met Brian this afternoon. What a little dude! Had a blast and wish him all the best for the future."
The swimmer was one of the home stars of Glasgow 2014, winning gold in the 200m and bronze in the 100m breaststroke, and has since added two silver medals to his collection in the same events at the European Championships in Berlin.