Surname Sienczak (Sienczak 
) , around the globe, is a rare family name. The last name Sienczak is characteristic of Poland, where it is a rare surname, Germany, where it is a very rare surname, and Spain, where it is an extremely rare surname. Measured by absolute frequency, the name is most common in Poland, Germany, and the United States. More prevalently, Sienczak is the forename as well as the last name.
| VARIANT | COUNTRY |
|---|---|
| Sienczak | Germany, United Kingdom, Spain, United States, Poland |