| Name | Membership No. | Grade | Branch |
|---|---|---|---|
| Tochukwu O Onuorah | SE 0831 | Member | Lagos |
| Felix Azubuike Onwujekwe | SE 0074 | Member | Enugu |
| Imo John Onyegbule | SE 0271 | Fellow | – |
| Eric Chiwuike Onyeiwu | SE 0272 | Member | Kaduna |
| Dr. Eleweke Onyejekwe | SE 0075 | Member | Owerri |
| Julius Okezue Onyeka | SE 0273 | Member | Owerri |
| Bernard Uchenna Onyerionwu | SE 0412 | Member | Lagos |
| Bobby Mathias Onyerionwu | SE 0480 | Member | Lagos |
| Innocent Osita Onyeyili | SE 0302 | Fellow | Enugu |
| Don Opara | SE 0220 | Member | Lagos |
| Peter A Opara | SE 0499 | Member | Abuja |
| Bassey Ika Oqua | SE 0210 | Member | Abuja |
| Godson Ikechukwu Oraedu | SE 0327 | Member | Lagos |
| Joshua C Orah | SE 0801 | Member | – |
| Prof. Cornelius O Orangun | SE 0045 | Fellow | Lagos |
| Charles Orebola Oresanwo | SE 0654 | Member | Lagos |
| Sesan Felix Oresegun | SE 0211 | Member | Ibadan |
| Bayode Julius Oribamise | SE 0447 | Member | Lagos |
| Ogheneale Umukoro Orie | SE 0725 | Member | Benin |
| Sunday Ade Orogade | SE 0783 | Member | Kaduna |
| Martins Osagie Osaghale | SE 0790 | Member | Lagos |
| Nonye Bernard Osakwe | SE 0502 | Member | Enugu |
| Lawrence Anie Osanebi | SE 0445 | Member | – |
| John Osawe | SE 0358 | Fellow | Benin |
| Osemeke Jude Oseafiana | SE 0809 | Member | Lagos |