It is believed that the Paleolithic man could have inhabited Montijo, as polished axes have been found in the site known as 'El Pedregal' and are preserved in the Archaeological Museum of Badajoz.

After the Romans conquered the judicial district in 25 B.C., they built the road that connected Mérida to Lisbon, crossing the lands of the Montijo area, and numerous rural villas dedicated to agriculture grew alongside it. Among them was the villa of TORREÁGUILA, built in 50 A.D., which reached its peak around the 3rd century A.D.

According to the historian Bernabé Moreno de Vargas, there was a Roman 'vicus' called AGLA in Montijo. If it existed, it would be the origin of Montijo, but it is nothing more than a theory that many doubt. Later, with the arrival of the Goths and Visigoths, they took advantage of the old Roman villas to build farmhouses and hermitages.

In what is now Plaza de España, there was a Visigothic construction well, which gave rise to the town's coat of arms with two trees and flanked by two maces. With the arrival of the Moorish troops to the judicial district, the inhabitants fled to take refuge in Mérida. In 1230, Mérida was conquered by Alfonso IX and with it, the region. The king granted the administration of the area to the Order of Santiago. The Order of Santiago took possession of the lands and founded the commandery of Montijo, appointing its first Commander, Juan Chacón.

The Knights of Santiago named the place Montejo, because it was born at the foot of a small hill that gave it its name, and granted charters and privileges for the area to be repopulated. Although, according to Bernabé Moreno de Vargas in his 'History of the city of Mérida' (1632), it was the Moors from Jaén who repopulated Montijo and gave it this name because they called Jaén 'Mentesa', from which the name Montijo would come.

The Commander's House was built on the highest part of the town, which would later be converted into a PALACE-HOUSE (now disappeared) by the Counts, in front of the first church in Montijo, that of San Isidro.

The urban area grew from this highest part of the town, around the Church of San Isidoro or Isidro. Among its narrow and winding streets, the inhabitants of Montijo settled, and among them, from the 13th to the 15th century, the Jews in the Peñas street.

On January 1, 1550, the town was sold to the Marquis of Villanueva del Fresno, D. Pedro Portocarrero, who founded the Lordship of Montijo. On December 13, 1599, by Royal Decree of Philip III, the Lordship of Montijo became a County, with its first Count being D. Juan Manuel Portocarrero y Osorio.

The Counts created the 'estates' of Montijo, annexing the nearby town of Puebla de la Calzada. The IV Count would build the GRANARY-HOUSE, the CONVENT OF THE CLARISAS, and make significant reforms in the Church of San Pedro and in the Palace-House.

Of special significance was Dª Mª Francisca de Sales Portocarrero, VI Countess of Montijo, whose son D. Cipriano Portocarrero had two daughters, Dª Eugenia, the famous Eugenia de Montijo, Empress of France by marriage to Napoleon III, and Dª Francisca, who married the Duke of Alba.

In 1569, a dispute with Mérida over the use of communal lands began, a dispute that would last until 1932 when it was settled.

Due to the war with Portugal, on May 22, 1644, the Portuguese looted and invaded Montijo, but four days later, on the feast of Corpus Christi, the battle of Montijo took place, where the Portuguese suffered a great defeat.

At the beginning of the 18th century, due to the War of Succession, there was intervention again with Portugal.

The early 19th century brought the war of Independence with France, and in June 1808, the French took the town, so the people of Montijo had to flee to Alburquerque. In 1812, the French left Montijo, leaving behind a desolate and ruined town.

In 1834, Montijo would come under the direct jurisdiction of the Governor of Badajoz, thus ending the jurisdiction of the Counts over the town. The disentailment (1835-1850) meant that the best lands auctioned off went to the richest.

The subhuman hygienic conditions led to a cholera epidemic in 1854, which had a great impact on the population. There were also locust plagues and years of drought, leading to a high unemployment rate among laborers by the end of the century, marking the beginning of peasant movements for the first time.

In the 20th century, local trade, previously meager, would receive a great boost. Culture also flourished, with two centers, the Casa del Pueblo, where workers organized into unions divided into guilds, and the artisans' circle, which brought together the artisanal, industrial, and commercial class.

On August 13, 1936, Lieutenant Colonel Yagüe took the town for General Franco's troops, and Montijo went from the Republic to the Dictatorship.

In the 1950s, the Badajoz Plan began (a project already conceived during the 2nd Republic), with the construction of the Montijo Canal by political prisoners imprisoned in militarized penal colonies and hired workers.