George, who was born July 22, wore a replica of an intricate lace-and-satin christening gown made for Queen Victoria's eldest daughter and first used in 1841.
When William was christened in 1982, he wore the original gown — by then well over a century old — but that gown has become so fragile that a replica was made.
The infant, who will head the Church of England when he becomes king, was christened with water from the River Jordan by Archbishop of Canterbury Justin Welby.
He arrived at the chapel in his father's arms with his mother by their side.
Kate, smiling broadly on her way into the chapel, wore a cream-colored Alexander McQueen dress and hat by milliner Jane Taylor with her long hair brushed to the side. William wore his customary dark suit and tie as he proudly carried their child.
Kate's parents Michael and Carole Middleton and her sister Pippa and brother James were also at the ceremony.
Pippa Middleton read from the Gospel of St. Luke and Prince Harry read from the Gospel of St. John. The two hymns were "Breathe on Me, Breath of God" and "Be Thou My Vision."
The chapel has a strong connection to William's mother, the late Princess Diana, whose coffin was laid before the chapel's altar for her family to pay their last respects in private before her 1997 funeral.
William and Kate also named seven godparents, who arrived at the chapel together.
They are: Oliver Baker, a friend from St. Andrews University; Emilia Jardine-Paterson, who went to the exclusive Marlborough College high school with Kate; Hugh Grosvenor, the son of the Duke of Westminster; Jamie Lowther-Pinkerton, a former private secretary to the couple; Julia Samuel, described as a close friend of Princess Diana; Zara Phillips, who is William's cousin; and William van Cutsem, a childhood friend of William.
Palace officials said water from the River Jordan — where Christians believe Jesus Christ was baptized — was used for the christening.
In the West Bank hours before the London christening, busloads of Russian tourists descended Wednesday morning on Qasr el-Yahud to immerse themselves in the River Jordan. The site — five miles (eight kilometers) east of Jericho — is considered Christianity's third holiest site after Bethlehem and Jerusalem.
The river's waters have often been used to make the sign of the cross on the heads of royal infants.
Some royal watchers camped outside the palace for more than 24 hours to obtain a good vantage point to watch the guests arrive, but the ceremony was private.
William and Kate hired photographer Jason Bell to take official pictures, which are expected to include a historic multi-generational photograph of the queen with three future monarchs: her son Charles, her grandson William and her great-grandson George.
The official photographs are expected to be released to the public on Thursday.
UPDATED: Please read and follow our commenting policy: