| City Hall | (956) 565-3114 |
| Administration | (956) 565-3114 ext.138 & 171 |
| Finance | (956) 565-3114 ext.163 |
| Utility Billing Dept | (956) 565-3114 ext.124 |
| Fire Department | (956) 565-7755 |
| Planning Department | (956) 565-3114 ext.128 |
| Human Resources Department | (956) 565-3114 ext.139 |
| Municipal Court | (956) 565-3114 ext.170 & 210 |
| Library | (956) 565-2371 |
| Waste Water Treatment Plant | (956) 565-0994 |
| Police Department | (956) 565-3102 |
| Public Works | (956) 565-6147 |
| Water Treatment Plant | (956) 565-2372 |
| Chamber of Commerce | (956) 565-2221 |
| Emergency Management | (956) 565-7755 |
| Mercedes Economic Development Corporation | (956) 565-2230 |
| Mercedes Independent School District | (956) 514-2000 |
