| Name | Participants | Dates | Stamps | ||
| 50 Years of Diplomatic R..etween Bulgaria and Cuba | 2 | (with Cuba) | 2010 | 4 | |
| Bird Migration - joint issue Bulgaria-Israel | 2 | (with Israel) | 2016 | 2 | |
| Black Sea Fauna & Flora | 2 | (with Ukraine) | 2017 | 4 | |
| Ecology - Balkan Mountai..nt issue Bulgaria-Serbia | 2 | (with Serbia) | 2009 | 4 | |
| Joint issue Armenia-Bulgaria | 2 | (with Armenia) | 2008 | 4 | |
| Joint issue Azerbaijan-Bulgaria | 2 | (with Azerbaijan) | 2016 | 2 | (incomplete) |
| Joint issue with Czech R..f the Arrival of St Cyri | 3 | (with Slovakia - Vatican City) | 2013 | 3 | |
| Romania and Bulgaria tog..t issue Bulgaria-Romania | 2 | (with Romania) | 2006 | 4 | (incomplete) |