Castilla comprises 34 barangays with an estimated population of 59,667. 27 of its barangays (79%) are connectivity dead zones with no recorded cell tower from either the national registry or crowdsourced data.
| Barangay | Population | Towers | Coverage |
|---|---|---|---|
| Amomonting | 1,798 | 0 | Dead zone: no towers from any source |
| Bagalayag | 539 | 0 | Dead zone: no towers from any source |
| Bagong Sirang | 571 | 0 | Dead zone: no towers from any source |
| Bonga | 685 | 0 | Dead zone: no towers from any source |
| Buenavista | 1,015 | 0 | Dead zone: no towers from any source |
| Burabod | 1,888 | 0 | Dead zone: no towers from any source |
| Caburacan | 1,008 | 0 | Dead zone: no towers from any source |
| Canjela | 651 | 0 | Dead zone: no towers from any source |
| Cogon | 1,023 | 0 | Dead zone: no towers from any source |
| Cumadcad | 7,373 | 12 | Crowdsourced signal only (no registered tower) |
| Dangcalan | 427 | 0 | Dead zone: no towers from any source |
| Dinapa | 3,070 | 0 | Dead zone: no towers from any source |
| La Union | 1,380 | 3 | Crowdsourced signal only (no registered tower) |
| Libtong | 1,481 | 0 | Dead zone: no towers from any source |
| Loreto | 951 | 0 | Dead zone: no towers from any source |
| Macalaya | 3,888 | 0 | Dead zone: no towers from any source |
| Maracabac | 316 | 0 | Dead zone: no towers from any source |
| Mayon | 2,261 | 0 | Dead zone: no towers from any source |
| Maypangi | 888 | 0 | Dead zone: no towers from any source |
| Milagrosa | 1,713 | 1 | Crowdsourced signal only (no registered tower) |
| Miluya | 1,093 | 0 | Dead zone: no towers from any source |
| Monte Carmelo | 662 | 0 | Dead zone: no towers from any source |
| Oras | 2,922 | 0 | Dead zone: no towers from any source |
| Pandan | 2,004 | 0 | Dead zone: no towers from any source |
| Poblacion | 3,104 | 0 | Dead zone: no towers from any source |
| Quirapi | 1,460 | 0 | Dead zone: no towers from any source |
| Saclayan | 412 | 0 | Dead zone: no towers from any source |
| Salvacion | 680 | 0 | Dead zone: no towers from any source |
| San Isidro | 5,000 | 7 | Crowdsourced signal only (no registered tower) |
| San Rafael | 2,179 | 2 | Crowdsourced signal only (no registered tower) |
| San Roque | 756 | 0 | Dead zone: no towers from any source |
| San Vicente | 3,383 | 3 | Crowdsourced signal only (no registered tower) |
| Sogoy | 2,236 | 4 | Crowdsourced signal only (no registered tower) |
| Tomalaytay | 850 | 0 | Dead zone: no towers from any source |