| Abbreviation | Definition |
|---|---|
| NARS | National Archives and Records Service |
| NASA | National Aeronautics and Space Administration |
| NBC | No Bloody Clue |
| NCIC | National Crime Information Center |
| NCIS | National Criminal Intelligence Service |
| NCPC | National Crop Protection Center |
| ND | Naval District |
| NEQ | Net Explosive Quantity |
| NF | Norfolk Field Office |
| NFIB | National Foreign Intelligence Board |
| NH | New Haven Field Office |
| NI | Not Identical |
| NI | Notoriety Index |
| NIA | National Intelligence Authority |
| NIBIN | National Integrated Ballistic Information Network |
| Nina | 9-Millimeter Handgun |
| NIS | Naval Investigative Service |
| NK | Newark Field Office |
| NO | New Orleans Field Office |
| NOC | Narcotics and Organized Crime |