After the success of the EMB 110 Bandeirante, Embraer began the development of their first transport category airliner in 1974. The so-called Family 12X comprised three models with modular concept designs: EMB 120 Araguaia, EMB 123 Tapajós and EMB 121 Xingu. EMB 121 was the sole 12X model effectively produced. Araguaia's name was changed to Brasilia in 1979 at the official launching of the project, when at a CAAA (Commuter Airline Association of America) convention at USA several suggestions from prospective operators were collected and incorporated to EMB 120 design. Thus, a completely new aircraft – no longer related to the 12X family – was launched. No common parts from EMB 121 Xingu were used, and the capacity was revised from 24 to 30 seats. Originally designed to utilise the new 1500 shp Pratt & Whitney PW115 turboprop, it was later upgraded to the 1892 eshp PW118.
The first aircraft entered service with Airnorth in October 1985. The basic EMB 120RT was upgraded to the extended range (1,575 km) EMB 120 ER, with older aircraft retrofitted via a Service Bulletin.
- EMB 120: Basic production version.
- EMB 120ER: Extended range and increased capacity version. All EMB-120ER S/Ns may be converted into the model EMB-120FC or into the model EMB-120QC.
- EMB 120FC: Full cargo version.
- EMB 120QC: Quick change cargo version.
- EMB 120RT: Transport version. All EMB-120RT S/Ns may be converted into the model EMB-120ER.
- VC-97: VIP transport version for the Brazilian Air Force.