This is one of five full-length portraits of members of the Brunswick family in the Royal Collection which were first attributed to van der Doort by Oliver Millar. They are all inscribed with the date of 1609. Prince Rudolf of Brunswick (1602-1616) was one of nine children and third son of Heinrich Julius, Duke of Brunswick-Lüneburg, Prince of Calenberg and Prince of Wolfenbüttel (1564-1613) and his second wife, Elisabeth, Princess of Denmark (1573-1625), eldest daughter of King Frederick II of Denmark and Norway (1534-1588). He was appointed Bishop of Halderstadt in 1615 but died the following year in Tübingen just before his thirteenth birthday and was buried there in the Collegiate Church of St George.

The young prince's costume is very similar to that worn by his older brother Christian (RCIN 404914), although here the black cloak is fully wrapped around the sitter's body. His white silk doublet is cut tight to the torso and his white silk breeches are voluminous. Both are decorated with vertical lines of gold braid. His crimson silk garters are tied into bows at each knee and matching shoe roses decorate the plain black shoes. His left hand rests on his sword hilt, his right on his hip. His collar is of the most translucent linen, starched and raised on a piccadil. A tall-crowned black hat decorated with a ornately jewelled hat badge is positioned on a table to the left.

Inscribed: H. RVDOLPHVS. / 1609