| Inns | HS |
| 225-8 | 37* | Ireland Under-19s v Afghanistan Under-19s | Cobham Oval (New), Whangarei | 2017/18 |
| 212 | 37 | Ireland Under-19s v Papua New Guinea Under-19s | Khulna Divisional Stadium, Khulna | 2003/04 |
| 204 | 31 | Ireland Under-19s v Zimbabwe Under-19s | Absa Puk Oval, Potchefstroom | 2023/24 |
| 191 | 47 | Ireland Under-19s v Kenya Under-19s | Gert Van Rensburg Stadium, Fochville | 1997/98 |
| 190 | 43 | Ireland Under-19s v England Under-19s | Haslegrave Ground, Loughborough | 2024 |
| 185-8 | 47 | Ireland Under-19s v Nepal Under-19s | Endeavour Park, Townsville | 2012 |
| 177-9 | 34 | Ireland Under-19s v Australia Under-19s | Colombo Cricket Club Ground, Colombo | 1999/00 |
| 163 | 45 | Ireland Under-19s v England Under-19s | Haslegrave Ground, Loughborough | 2023 |
| 159-9 | 35 | Ireland Under-19s v Sri Lanka Under-19s | Christian Brothers School Ground, Boksburg | 1997/98 |
| 158 | 42 | Ireland Under-19s v South Africa Under-19s | Brian Lara Stadium, Tarouba | 2021/22 |
| 154-9 | 45 | Ireland Under-19s v West Indies Under-19s | Institute Perguruan Temenggong Ibrahim, Johor | 2007/08 |
| 153 | 21 | Ireland Under-19s v Pakistan Under-19s | Avion Park Cricket Club, Kempton Park | 1997/98 |
| 149 | 46 | Ireland Under-19s v Sri Lanka Under-19s | Allan Border Field, Brisbane | 2012 |
| 142 | 35* | Ireland Under-19s v Pakistan Under-19s | Khulna Divisional Stadium, Khulna | 2003/04 |
| 142-4 | 33 | Ireland Under-19s v Canada Under-19s | Sheikh Kamal International Cricket Stadium, Cox's Bazar | 2015/16 |
| 141 | 34 | Ireland Under-19s v Bangladesh Under-19s | Chittagong Divisional Stadium, Chittagong | 2003/04 |
| 141 | 34 | Ireland Under-19s v England Under-19s | Haslegrave Ground, Loughborough | 2024 |
| 134 | 39 | Ireland Under-19s v Sri Lanka Under-19s | Sinhalese Sports Club Ground, Colombo | 1999/00 |
| 133 | 32 | Ireland Under-19s v India Under-19s | Brian Lara Stadium, Tarouba | 2021/22 |
| 131-9 | 30* | Ireland Under-19s v Nepal Under-19s | Khan Shaheb Osman Ali Stadium, Fatullah | 2015/16 |
| 129 | 36 | Ireland Under-19s v Bangladesh Under-19s | Welagedara Stadium, Kurunegala | 1999/00 |
| 129 | 31 | Ireland Under-19s v Australia Under-19s | Endeavour Park No 2, Townsville | 2012 |
| 129-6 | 42 | Ireland Under-19s v Namibia Under-19s | WEP Harris Oval, Brisbane | 2012 |
| 127-5 | 43 | Ireland Under-19s v Namibia Under-19s | Moors Sports Club Ground, Colombo | 1999/00 |
| 123 | 31 | Ireland Under-19s v Bangladesh Under-19s | Bayuemas Oval, Kuala Lumpur | 2007/08 |
| 122-7 | 43 | Ireland Under-19s v Papua New Guinea Under-19s | MainPower Oval, Rangiora | 2017/18 |
| 122 | 40 | Ireland Under-19s v United Arab Emirates Under-19s | Queen's Park Oval, Port of Spain | 2021/22 |
| 119-4 | 48 | Ireland Under-19s v Papua New Guinea Under-19s | Lenasia Stadium, Johannesburg | 1997/98 |
| 118 | 37 | Ireland Under-19s v Zimbabwe Under-19s | Isolation | 2021/22 |
| 116-4 | 27 | Ireland Under-19s v Namibia Under-19s | Nondescripts Cricket Club Ground, Colombo | 2005/06 |
