Zajączkowo was formerly part of the German Empire. In the German Empire, the place was called Seinskau.
The place is now called Zajączkowo and belongs to Poland.
| Historical place name | Country | Administration | Time |
|---|---|---|---|
| Zajonskowo | German Empire | Löbau | before the Versailles Treaty |
| Jazonczkowo | German Empire | Löbau | before the Versailles Treaty |
| Zajączkowo | Poland | Lubawa | after the Versailles Treaty |
| Seinskau | German Empire | Neumark (Westpr.) | 1939 |
| Zajączkowo | Poland | Nowe Miasto Lubawskie | 1945 |
| Zajączkowo | Poland | Toruń | 1992 |