The town was previously known as Masilao (from Tagalog masilaw, "dazzling"), named after the glaring red flowers of the dapdap plant (Erythrina variegata) common in the area.

It was separated to become an independent town named Amadeo on July 15, 1872, care of Governor-General Rafael Izquierdo y Gutiérrez.

It initially consisted of eight barangays, all formerly of Silang town: Halang, Pangil, Banaybanay, Bukal, Maitim, Minantok, Salaban, and Talon.

[9] On February 15, 1989, Mayor Jeremias Villanueva and his security man Virgilio Lascano were assassinated by three gunmen riding a vehicle in front of his rented townhouse in Las Piñas, Metro Manila.

[10] Four suspects, including a Manila policeman from Amadeo, were later captured in Parañaque a month later on March 16,[11] and by next day, the National Bureau of Investigation (NBI) confirmed that the assassination was ordered by Villanueva's political rival, former Mayor Reynaldo Bayot.