Kozły-Janowo was formerly part of the German Empire. In the German Empire, the place was called Kozly Janowo.
The place is now called Kozły-Janowo and belongs to Poland.
| Historical place name | Country | Administration | Time |
|---|---|---|---|
| Kozly Janowo | Russian Empire | Mlava | 1914 |
| Kozły-Janowo | Poland | Mława | 1919 |
| Kozly Janowo | German Empire | Mielau | 1939 |
| Kozły-Janowo | Poland | Mława | 1945 |
| Kozły-Janowo | Poland | Ciechanów | 1992 |