Roger Speed was greeted in Lyon by Wales fans chanting his name ahead of the Euro 2016 semi-final with Portugal.
The match kicks off at 20:00 BST on Wednesday, with the winner facing France or Germany in the final.
Mr Speed said: "I'm very very proud, I know all the lads and they think about him [Gary Speed] all the time - let's do it for Speedo!"
Former Leeds United, Everton and Newcastle United midfielder Speed was found hanged in the garage of his home in Huntington, Chester, in November 2011.
His father told Good Morning Wales: "It's a very emotional day. He's done a great job, Chris [Coleman], I wished him all the best - he's done a great job to get them where they are."
Mr Speed was spotted in a restaurant by Wales fans in Lyon on the eve of the match and was met with chants of "there's only one Roger Speed".
"The fans were brilliant - it's unbelievable," he added.
He is also optimistic about the team's chances against Portugal - who are yet to win a match without going to penalties at the tournament.
"I think we'll go to the final, no doubts. The way the lads are playing, I think they're the best team there."
Asked what his son would make of Wales' achievements, he replied: "He'd be as proud as we are."
The father of the late Wales manager Gary Speed has said today is "emotional" for his family.