The 22-year-old admits he is "honoured" to be part of the Portugal set-up in Brazil as his side prepare for their opening clash with Germany
The 22-year-old Sporting midfielder only made his senior Seleccao debut in Novemeber last year in the victorious play-off second leg against Sweden and was one of the more surprising inclusions in Paulo Bento's final 23-man party for Brazil.
Despite his impressive club form in the Primeira Liga, which has seen him linked with Premier League giants Liverpool, Manchester City and Manchester United in recent months, William Carvalho says his call-up was still a shock.
"At the start of the season I just didn't expect to be here, though I put in some good performances for Sporting and I'm about to do what every player dreams of: play in a World Cup," he told Fifa.com.
Another Portugal midfielder set to make his World Cup debut is the vastly more experienced Joao Moutinho, who has earned 68 caps for his country but has never performed on the biggest international stage, having been overlooked for selection for South Africa 2010.
"Obviously it's a great honour for me to be in Brazil," said the Monaco playmaker. "God intended for this to be my first world finals."
Portugal face Germany in their opening Group G match on Monday.