He was baptised in Charles XI's baptismal font, which stood on Gustav III's carpet and he lay in Charles XI's cradle with Oscar II's crown beside him.His godparents were the Crown Prince and Crown Princess of Denmark (his paternal uncle and aunt), the Crown Prince of Norway, Princess Juliana of the Netherlands, the King of Sweden (his patrilineal great-grandfather), the Hereditary Prince of Saxe-Coburg and Gotha (his maternal uncle), the Crown Prince and Crown Princess of Sweden (his paternal grandfather and step-grandmother), and Count Folke and Countess Maria Bernadotte af Wisborg.
He was christened at the Royal Chapel on 7 June 1946 by the Archbishop of Uppsala, Erling Eidem.
He is the youngest child and only son of Prince Gustaf Adolf, Duke of Västerbotten, and Princess Sibylla of Saxe-Coburg and Gotha.
His father died on 26 January 1947 in an airplane crash in Denmark when Carl Gustaf was nine months old.
His father's death had left the nine-month-old prince second in line for the throne, behind his grandfather, then Crown Prince Gustaf Adolf.
When his great-grandfather Gustaf V died in 1950, the four-year-old prince became the heir apparent of Sweden.