3 Anti-Aircraft Brigade was formed on the 7 December 1938 at Belfast. It went to France with the BEF in November 1939. It returned to Belfast in June 1940 serving there under 12 Anti-Aircraft Division and 7 Anti-Aircraft Group. 3 Anti-Aircraft Brigade was incorporated into 7 Anti-Aircraft Group and formally disbanded in September 1944.
Illustrations of the formation badges under which a unit served or supported are given. This is no guarantee that the unit used this formations badge.
| Dec 38 | Belfast |  | 3 Anti-Aircraft Division |
| Nov 39 | France | | B.E.F. |
| Jun 40 | Belfast | | Home Forces |
| Nov 40 | Belfast |  | 12 Anti-Aircraft Division |
| Oct 42 | Belfast – Brigade incorporated into 7 AA Group
and disappeared although not formally
disbanded until September 1944 |  | 7 Anti-Aircraft Group |
Order of Battle December 1938
| 8 (Belfast) Anti-Aircraft Regiment (21, 22, 23 & 5 LAA Batteries) |
| 8 (Londonderry) Anti-Aircraft Regiment (24, 25, 26 & 6 LAA Batteries) |
| 102 Anti-Aircraft Regiment (314, 315, 316 & 174 LAA, 175 LAA Batteries) |
| 3 (Ulster) Searchlight Regiment (9, 10, 11, 12 Batteries) |
Order of Battle November 1939
| 2 Anti-Aircraft Regiment |
| 4 Anti-Aircraft Regiment |
| 2 Independent Light Anti-Aircraft Battery |
| 4 Independent Light Anti-Aircraft Battery |
| 165 Light Anti-Aircraft Battery from 54 LAA Regiment |
Order of Battle May 1940
| 2 Anti-Aircraft Regiment (4, 5, 6 Batteries) |
| 8 (Belfast) Anti-Aircraft Regiment (21, 22, 23 Batteries) |
| 79 (Herts Yeo) Anti-Aircraft Regiment (246, 247, 248 Batteries) |
| 4 Independent Light Anti-Aircraft Battery |
| 174 Light Anti-Aircraft Battery from 58 LAA Regiment |
Order of Battle 1940-41
| 102 Heavy Anti-Aircraft Regiment (314, 315, 316 Batteries) |
| 66 Light Anti-Aircraft Regiment (175, 176, 251 Batteries) |
| 90 Searchlight Regiment (546, 548, 560 Batteries) |
| 91 Searchlight Regiment (549, 550, 552, 553 Batteries) |
Order of Battle 1941-42
| 1 Heavy Anti-Aircraft Regiment (1, 2, 17 Batteries) |
| 102 Heavy Anti-Aircraft Regiment (314, 315, 316, 431 Batteries) |
| 111 Heavy Anti-Aircraft Regiment (347, 355, 356, 389 Batteries) |
| 66 Light Anti-Aircraft Regiment (175, 176, 251, 459 Batteries) |
| 81 Light Anti-Aircraft Regiment (199, 261, 307, 472 Batteries) |
| 84 Light Anti-Aircraft Regiment (177, 201, 251, 448 Batteries) |
| 146 AA Z Battery |
| 90 Searchlight Regiment (546, 548, 560 Batteries) |
| 91 Searchlight Regiment (549, 550, 551, 552 Batteries) |
