"The judges and court personnel will leave Moscow on May 12," the spokesperson said, adding that all 19 judges and 30 out of 250 members of staff had agreed to follow the court to Russia's second city.
Almost all the court's archives and documentation have already been transferred to the city, and suits are already being sent there.
The relocation, which began on February 1, is to be completed by May 21. The Constitutional Court will occupy the reconstructed 19th-century buildings of the Senate and the Synod, overlooking the Bronze Horseman statue of Peter the Great and the Neva River in the center of St. Petersburg. The court's first session is to take place on May 22.
The idea to relocate the court was originally put forward by St. Petersburg governor, Valentina Matvienko, who was backed by the city's legislature. Federal parliament approved it in late 2006, and President Vladimir Putin signed a decree on its transfer in December 2007.
Putin, who was born in St. Petersburg, earlier said that while the city was often called Russia's second capital, it was unable to boast political or judicial establishments worthy of the status this implied.
Proponents of the idea also said the decision would help curb corruption and channel more federal funds into St. Petersburg.
Members of the Constitutional Court earlier opposed the move, saying the court could lose qualified staff, and the change of location could damage its efficiency.
The court will retain a representative office and a press office in Moscow.
There are plans to show Constitutional Court sessions in St. Petersburg live in the Internet.
Earlier reports said measures to relocate the court and its members of staff would cost at least 221 million rubles ($9.5 million), plus expenses for the reconstruction of the buildings to accommodate the court and the construction of housing for judges and other personnel.