Isabela has 1055 barangays across 37 municipalities. 700 barangays (66%) are connectivity dead zones.
| Municipality | Barangays | Dead zones |
|---|---|---|
| Alicia | 34 | 15 (44%) |
| Angadanan | 59 | 58 (98%) |
| Aurora | 33 | 17 (52%) |
| Benito Soliven | 29 | 27 (93%) |
| Burgos | 14 | 5 (36%) |
| Cabagan | 26 | 16 (62%) |
| Cabatuan | 22 | 9 (41%) |
| City of Cauayan | 65 | 22 (34%) |
| City of Santiago | 37 | 8 (22%) |
| Cordon | 26 | 16 (62%) |
| Delfin Albano (Magsaysay) | 29 | 23 (79%) |
| Dinapigue | 6 | 6 (100%) |
| Divilacan | 12 | 12 (100%) |
| Echague | 64 | 42 (66%) |
| Gamu | 16 | 8 (50%) |
| Ilagan City (Capital) | 91 | 55 (60%) |
| Jones | 42 | 39 (93%) |
| Luna | 19 | 17 (89%) |
| Maconacon | 10 | 10 (100%) |
| Mallig | 18 | 13 (72%) |
| Naguilian | 25 | 18 (72%) |
| Palanan | 17 | 17 (100%) |
| Quezon | 15 | 8 (53%) |
| Quirino | 21 | 19 (90%) |
| Ramon | 19 | 10 (53%) |
| Reina Mercedes | 20 | 12 (60%) |
| Roxas | 26 | 12 (46%) |
| San Agustin | 23 | 22 (96%) |
| San Guillermo | 26 | 26 (100%) |
| San Isidro | 13 | 4 (31%) |
| San Manuel | 19 | 5 (26%) |
| San Mariano | 36 | 31 (86%) |
| San Mateo | 33 | 19 (58%) |
| San Pablo | 17 | 13 (76%) |
| Santa Maria | 20 | 14 (70%) |
| Santo Tomas | 27 | 23 (85%) |
| Tumauini | 46 | 29 (63%) |