Daniel began his professional career in the Swedish Hockey League with Modo Hockey in 1997 and was co-recipient, with Henrik, of the 1999 Golden Puck as Swedish player of the year. He played four seasons with Modo (including a return in 2004–05 due to the NHL lockout), helping the club to two consecutive appearances in the Le Mat Trophy Finals, in 1999 and 2000, where they lost both times. Selected second overall by the Canucks in the 1999 NHL Entry Draft, Daniel moved to the NHL in the 2000–01 season. He spent his entire NHL career in Vancouver, and in 2016 became the club's all-time top goal scorer. After emerging as a top player in the club during the 2005–06 season, Daniel since recorded six consecutive campaigns of at least 20 goals and 70 points. In 2011, he won the Art Ross Trophy as the League's leading point-scorer and the Ted Lindsay Award as the best player in the League, as voted by fellow players. Daniel was also nominated for the Hart Memorial Trophy as the League's most valuable player. In Sweden, he and Henrik were awarded the Victoria Scholarship as the country's athletes of the year.
Daniel was born on 26 September 1980, in Örnsköldsvik, Sweden, six minutes after his identical twin brother, Henrik. The pair have two older brothers, Stefan and Peter. Their father, Tommy, is a school vice-principal and also played for Modo Hockey in the 1960s, while his mother, Tora, is a nurse. Daniel began playing organized hockey with Henrik when they were eight. They did not regularly play on the same line until Daniel switched from centre to wing at 14. Daniel and Henrik both attended high school at the Nolaskolan Gymnasium in Sweden while playing professionally for Modo.