| ITF W60 Shrewsbury | 02/12 18:10 | 25 | [369] Jodie Anna Burrage v Valentini Grammatikopoulou [171] | 6-3,3-0 | |
| 2019 Fed Cup | 02/09 12:00 | 28 | [171] Valentini Grammatikopoulou v Berfu Cengiz [331] | 3-4 | |
| 2019 Fed Cup | 02/08 16:30 | - | [171] Valentini Grammatikopoulou v Kaja Juvan [169] | 7-6,5-7,6-3 | |
| 2019 Fed Cup | 02/07 16:30 | - | [83] Katie Boulter v Valentini Grammatikopoulou [171] | 6-3,4-6,6-3 | |
| 2019 Fed Cup | 02/06 16:30 | - | [311] Dalma Galfi v Valentini Grammatikopoulou [171] | 6-0,6-3 | |
| WTA St. Petersburg | 01/26 18:55 | 45 | [173] Valentini Grammatikopoulou v Jana Fett [218] | 1-6,1-6 | |
| Australian Open Women | 01/10 06:55 | 45 | [107] Bianca Andreescu v Valentini Grammatikopoulou [173] | 6-4,6-1 | |
| Australian Open Women | 01/09 05:05 | 44 | [173] Valentini Grammatikopoulou v Irina Bara [155] | 6-3,6-2 | |
| ITF W25 Hong Kong | 01/04 03:45 | 27 | [172] Valentini Grammatikopoulou v Barbora Stefkova [300] | 5-7,3-6 | |
| ITF W25 Hong Kong | 01/03 06:45 | 26 | [172] Valentini Grammatikopoulou v Hiroko Kuwata [269] | 6-4,0-6,7-6 | |
| ITF W25 Hong Kong | 01/02 06:15 | 25 | Valentini Grammatikopoulou v Ho Ching Wu | 6-1,6-4 | |
| ITF Women Dubai | 12/10 09:40 | - | [104] Mandy Minella v Valentini Grammatikopoulou [172] | 6-1,6-4 | |
| WTA Taipei | 11/15 09:30 | 26 | [160] Valentini Gram'lou v En Shuo Liang [276] | 3-6,1-6 | |
| WTA Taipei | 11/14 03:00 | 25 | Kwan Yau Ng v Valentini Gram'lou | 2-6,2-6 | |
| WTA Taipei | 11/14 03:00 | 25 | [41] Saisai Zheng v Valentini Gram'lou [160] | Cancelled | |
| ITF Women Shenzhen | 11/09 04:05 | - | [46] Saisai Zheng v Valentini Grammatikopoulou [165] | 6-2,6-1 | |
| ITF Women Shenzhen | 11/08 04:15 | - | [191] Elena Rybakina v Valentini Grammatikopoulou [165] | 4-6,6-3,3-6 | |
| ITF Women Shenzhen | 11/06 04:15 | - | [165] Valentini Grammatikopoulou v Nao Hibino [119] | 6-3,6-4 | |
| WTA Mumbai | 11/02 14:35 | - | [165] Irina Khromacheva v Valentini Grammatikopoulou [171] | 7-5,4-6,6-1 | |
| WTA Mumbai | 10/31 10:30 | 26 | [171] Valentini Grammatikopoulou v Deniz Khazaniuk [252] | 6-3,4-6,6-4 | |
| WTA Mumbai | 10/30 09:05 | 25 | Kwan Yau Ng v Valentini Grammatikopoulou | 0-6,2-6 | |
| WTA Moscow | 10/17 10:45 | 26 | [170] Valentini Grammatikopoulou v Anastasia Pavlyuchenkova [40] | 5-7,0-6 | |
| WTA Moscow | 10/15 08:00 | 54 | [101] Ons Jabeur v Valentini Grammatikopoulou [170] | 7-5,6-1 | |
| WTA Moscow | 10/14 09:00 | 46 | [171] Valentini Grammatikopoulou v Georgina Garcia-Perez [126] | 6-1,6-2 | |
| WTA Moscow | 10/13 07:00 | 45 | [171] Valentini Grammatikopoulou v Alexandra Panova [477] | 6-7,6-4,6-4 | |
| WTA Linz | 10/09 14:00 | 25 | [97] Kristyna Pliskova v Valentini Gramma'poulou [171] | 6-4,6-2 | |
| WTA Linz | 10/08 09:00 | 46 | [171] Valentini Gramma'poulou v Vitalia Diatchenko [117] | 6-2,7-5 | |
| WTA Linz | 10/07 12:10 | - | [88] Carina Witthoeft v Valentini Gramma'poulou [172] | 7-6,2-6,3-6 | |
| ITF Women Valencia | 09/26 12:30 | - | [291] Andrea Gamiz v Valentini Grammatikopoulou [171] | 3-6,6-4,6-2 | |
| ITF Women Zagreb | 09/06 11:05 | - | Kaja Juvan v Valentini Grammatikopoulou | 6-3,6-2 |