Argos-Shimano rider Kittel, who also won the opening stage and came second on stage two, sprinted to victory ahead of Vacansoleil-DCM teammates Kenny van Hummel and Danny van Poppel.
That sprint finish gave Kittel victory over stage two winner Bryan Coquard of Europcar by seven seconds, with Coquard finishing 12th in the 171km final stage.
In the day's other action Amets Txurruka of Caja Rural won the Vuelta a Asturias, adding overall victory to his stage one win on Saturday after finishing in the leading pack on the second and final stage.
Movistar's Javier Moreno won the second stage in a sprint ahead of Mikel Landa and Andre Cardoso.
"It's one of the wins I will always remember," said Txurruka.
Finally, Sebastien Delfosse of Crelan-Euphony won the Rund um Koln in Germany, with Pieter Jacobs second and Georg Preidler third.
Tour de Picardie stage three results
1. Marcel Kittel (Ger) Team Argos-Shimano
2. Kenny Robert van Hummel (Ned) Vacansoleil-DCM Pro Cycling Team
3. Danny van Poppel (Ned) Vacansoleil-DCM Pro Cycling Team
4. Adrien Petit (Fra) Cofidis, Solutions Credits
5. Jens Debusschere (Bel) Lotto Belisol
Tour de Picardie final GC
1. Marcel Kittel (Ger) Team Argos-Shimano 13:08:44
2. Bryan Coquard (Fra) Team Europcar +7"
3. Kenny Robert van Hummel (Ned) Vacansoleil-DCM Pro Cycling Team +20"
4. Sébastien Minard (Fra) AG2R La Mondiale "
5. Sven Vandousselaere (Bel) Topsport Vlaanderen-Baloise +21"