01 Apr2025 | Shelbourne | Woking | Free agent | |
08 Dec2024 | Shrewsbury | Shelbourne | Free agent | |
| - | Sutton | Shrewsbury | Return from loan | |
08 Jan2023 | Shrewsbury | Sutton | Loan | |
| - | Gillingham | Shrewsbury | Return from loan | |
| - | Shrewsbury | Gillingham | Loan | |
07 Jan2022 | Portsmouth | Shrewsbury | Free agent | |
| - | Sunderland | Portsmouth | Free agent | |
| - | Millwall | Sunderland | Free agent | |
| - | Torquay | Millwall | Return from loan | |
| - | Millwall | Torquay | Loan | |
| - | Aldershot | Millwall | Return from loan | |
| - | Millwall | Aldershot | Loan | |
| - | Crawley | Millwall | Return from loan | |
| - | Millwall | Crawley | Loan | |
04 Oct2012 | Hayes & Yeading | Millwall | Return from loan | |
03 Sept2012 | Millwall | Hayes & Yeading | Loan | |
02 Jan2012 | Staines | Millwall | Return from loan | |
10 Jan2011 | Millwall | Staines | Loan |
A. O'Brien transfer history tracks all club moves during the professional career, including transfer dates and teams involved.