The German father, French mother, child, and the ship's captain were allegedly kidnapped late Sunday night and moved to an undisclosed mountainous area on shore, chief administrator from the city of Las Korey in the Puntland region of Somalia, Jama Dabeed told news agency DPA.
The Foreign Office in Berlin said it is working to clarify the situation. So far there is no information as to whether the pirates have demanded a ransom for the family.
Waters off the coast of the horn of Africa - particularly near Somalia and Tanzania - are known to be frequented by pirates, which operate much like organized crime rings.
In 2007, officials recorded 263 pirate attacks, an increase of 10 percent from the previous year. Worldwide damages from pirate attacks are estimated at up to €13 billion.