In April 1948, during the 1947–48 Civil War in Mandatory Palestine, the kibbutz was the epicenter of the Battle of Mishmar HaEmek, successfully repelling the first major offensive of the Arab Liberation Army commanded by Fawzi al-Qawuqji.

Mishmar HaEmek is located in the southwestern part of the Jezreel Valley, between Highway 66 to its northeast and the foot of the Menashe Heights to its southwest.

They were Polish Jews from Galicia and were members of three groups who graduated from HaShomer HaTzair movement, one from the town of Afula and two from the Jerusalem area.

On 21 January 1922, they, along with some unaffiliated people, joined in the Neve Sha'anan neighborhood of Haifa to form the gar'in (Hebrew: גרעין, lit.

Initially, only 15 men and women left Afula to Abu Shusha and settled in a nearby khan, from where they began preparing for agricultural work.

British policemen ordered the kibbutz to evacuate and promised to take care for their property, and so the members left the following day.

[5] It operated as a boarding school and put into practice HaShomer HaTzair's socialist ideology, creating an independent "children's society."

[20] In the following years, in addition to the school, the members also constructed a water tower, built a cowshed, planted a vineyard and various fruit trees and dug wells.

The Jewish National Fund and Worton Hall Studios made a 1947 movie called The Great Promise (Dim'at Ha'Nehamah Ha'Gedolah), and a number of scenes were filmed in the kibbutz.

[26] British High Commissioner Arthur Grenfell Wauchope visited the kibbutz and appointed 15 members as armed guards; however, in August 1936, the situation worsened when the attacks became more frequent.

[18] Poet and future Israeli politician Uri Zvi Greenberg criticized the members of Mishmar HaEmek for not taking matters into their hands after the attacks on their fields.

[27] In that period the Palmach (an elite force of the Jewish Haganah underground organization) used the trees in the nearby forest as cover for their main training camp and its fighters worked in the kibbutz so not to raise suspicion by the British soldiers.

[31] The leader of the ALA, Fawzi al-Qawuqji, planned to seize Mishmar HaEmek to control the route between Jenin and Haifa.

[33] During the shelling of the kibbutz, houses were destroyed, civilians, defenders, and animals were killed and the prominent school building was heavily damaged.

The ALA sent terms to the Haganah, saying they would lift the siege of the kibbutz, regroup and move toward Haifa if the Jewish forces would not retaliate against the nearby Arab villages in return.

In the night between 8–9 April, the Jewish forces launched a counter-attack under the command of Yitzhak Sadeh and captured the nearby Arab village of Al-Ghubayya al-Fawqa in a fierce battle.

In the next days, troops of the Carmeli Brigade and the Palmach unit captured several other villages near Mishmar HaEmek and nearby Ein HaShofet, and destroyed them all.

[37] In May 1950 a village and ma'abara (immigrant transit camp) called Keren Yesha was established by the Jewish Agency for Yemeni Jews next to Mishmar HaEmek.

The Hed Ha-Mizrach newspaper described life in Keren Yesha two months after its establishment; the Yemeni immigrants lived in tents and although the residents claimed to be content, they also said that there was not enough support by the authorities.

In an attempt to save the kibbutz from bankruptcy, Tama began manufacturing plastic netting used for bundling crops and in the late 1980s the crisis ended.

Several successful business moves by Tama in the early 1990s led the kibbutz to an era of economic prosperity and high quality of life.

Prosperity led the kibbutz to increase the salaries of its members, to create personal funds for families, and to institutionalize culture and recreation activities thanks to the weekly labor days, reduced to five.

Many leaders of the Israeli left participated in the parade including former politicians Ya'akov Hazan (91 years old at the time) and Emri Ron, both hailing from Mishmar HaEmek, Elisha Shapira the head of Kibbutz Arzi, and Rafael Eitan and Hagai Meirom, both members of the Knesset (Israel's parliament).

[46]In 2010 the kibbutz decided, after a series of public meetings, to appoint a team of members to discuss the privatization of electricity, food, mail, barbershop and cosmetics.

[58] In 2019 the kibbutz finalized a deal with the kibbutzim of Evron and Sa'ar to buy a quarter of their share of a company called Bermad, estimated to be worth around 450 million NIS.

[63] 41.4% of the residents older than 15 worked in manufacturing, 16.4% in education, 11.6% in agriculture, 7.9% in community, social, personal and other services, and 5.4% in real estate, renting and business activities.

[20] The complex of the Shomeria School continued to serve the kibbutz for informal education,[20] and following a renovation it now houses offices and a library.

Among the discoveries are the remains of an earth ramp around the mound dated to the Middle Bronze Age, and underground stores attributed to the Crusader period.

[69] Artifacts from Tel Shush are displayed in a permanent, free-access exhibition prepared by members of the kibbutz and with aid from the Israel Antiquities Authority.

Remains of a Yarmukian culture included flint sickle blades, saws and arrowheads as well as a likely tomb with human bones, some inside a jar.