| Challenger Augsburg | 08/20 14:10 | 14 | [416] Daniel Masur v Constantin Frantzen [98] | 6-3,6-4 | |
| Challenger Drummondville | 11/15 20:45 | 25 | Roko Horvat v Constantin Frantzen | 7-6,6-1 | |
| Challenger Drummondville | 11/14 15:00 | 19 | Constantin Frantzen v Roy Smith | 6-7,6-7 | |
| Challenger Drummondville | 11/13 16:35 | 14 | [474] Omni Kumar v Constantin Frantzen [207] | 6-2,5-7,5-7 | |
| ITF M25 Harlingen | 10/18 23:30 | 19 | Constantin Frantzen v Drew Van Orderlain | 3-6,4-6 | |
| Challenger - Columbus | 09/18 16:00 | 14 | [283] Constantin Frantzen v James Trotter [404] | 0-6,2-6 | |
| ITF M25 Marburg | 07/07 10:15 | 26 | Constantin Frantzen v Milan Welte | 6-3,5-7,1-6 | |
| ITF M25 Marburg | 07/06 10:40 | 25 | Taym Al Azmeh v Constantin Frantzen | 6-7,1-6 | |
| ITF M25 Marburg | 07/05 09:45 | 54 | Milan Welte v Constantin Frantzen | 4-6,6-3,5-10 | |
| ITF M25 Marburg | 07/04 11:30 | 54 | Constantin Frantzen v Daniel Siniakov | 6-4,6-3 | |
| ITF M25 Arlon | 06/22 08:00 | 25 | Constantin Frantzen v Alexander Hoogmartens | 4-6,1-6 | |
| ITF M25 Arlon | 06/21 08:00 | 54 | [447] Tim Sandkaulen v Constantin Frantzen [423] | 6-1,4-6,8-10 | |
| ITF M25 Arlon | 06/20 10:40 | 54 | Victor Ernaelsteen v Constantin Frantzen | 3-6,2-6 | |
| ITF M15 Meerbusch | 05/02 08:00 | 62 | Constantin Frantzen v Marco De Rossi | 3-6,2-6 | |
| ITF M15 Meerbusch | 05/01 07:30 | 62 | Constantin Frantzen v Mihailo Kecojevic | 6-3,6-3 | |
| ITF M25 Split | 04/25 10:20 | 62 | Drazen Petrovic v Constantin Frantzen | 6-4,7-5 | |
| ITF M15 Monastir | 04/06 12:35 | 25 | Constantin Frantzen v Szymon Kielan | 3-6,5-7 | |
| ITF M25 Monastir | 04/04 13:30 | 62 | Constantin Frantzen v Jakub Katuch | 6-3,6-0 | |
| ITF M25 Monastir | 04/04 09:00 | 62 | Constantin Frantzen v Matthew Stubbings | 6-1,6-2 | |
| ITF M25 Monastir | 03/27 10:00 | 62 | Constantin Frantzen v Pol Wattanakul | 6-7,7-5,8-10 | |
| ITF M25 Monastir | 03/23 07:30 | 62 | Louis Herman v Constantin Frantzen | 6-2,6-1 | |
| ITF M25 Monastir | 03/20 09:00 | 62 | Constantin Frantzen v Alexandre Aubriot | 6-3,6-3 | |
| ITF M25 Trimbach | 03/17 09:00 | 26 | Johannes Haerteis v Constantin Frantzen | 6-3,6-7,6-2 | |
| ITF M25 Trimbach | 03/16 13:55 | 25 | Constantin Frantzen v Leonardo Taddia | 6-4,7-5 | |
| ITF M25 Trimbach | 03/15 09:00 | 54 | Constantin Frantzen v Laurin Aerne | 3-6,7-6,12-10 | |
| ITF M25 Trimbach | 03/14 09:00 | 54 | Constantin Frantzen v Jasin Jakupi | 6-3,6-3 | |
| ITF M25 Glasgow | 02/17 10:00 | 26 | Anton Matusevich v Constantin Frantzen | 6-4,6-2 | |
| ITF M25 Glasgow | 02/15 10:00 | 25 | Felix Gill v Constantin Frantzen | 7-6,4-6,0-6 | |
| ITF M25 Glasgow | 02/14 09:55 | 54 | Osgar O'Hoisin v Constantin Frantzen | 3-6,2-6 | |
| ITF M25 Glasgow | 02/13 11:00 | 54 | Oliver Tarvet v Constantin Frantzen | Retired |