Thatcher was born in Sangamon County, Illinois, to Hezekiah Thatcher and Alena Kitchen. The Thatcher family joined the Church of Jesus Christ of Latter Day Saints in 1843, and moved to Macedonia, Illinois, and later to Nauvoo. Together, with the main body of the church, they began their trek westward in 1846 and arrived in the Salt Lake Valley in September 1847.^{[1][citation needed]}

Hezekiah and Alena, with seven of their eight living children (including Thatcher), departed for California in 1849, seeking to acquire wealth through the Gold Rush. They returned to Utah Territory in 1857. Thatcher served a mission for the church at age 15, from which he returned in 1858. In 1859, the family settled in Cache Valley, where Thatcher helped Hezekiah locate canal and mill sites.^{[1][citation needed]}

From 1860 to 1861, Thatcher studied at the University of Deseret. From 1866 to 1868, he served a second mission, this one to the United Kingdom and France. He later served as the church's first mission president in Mexico.^{[1][citation needed]}

Thatcher became an apostle and a member of the Quorum of the Twelve Apostles in April 1879.^{[citation needed]} He replaced Orson Hyde, who died on November 28, 1878.^{[citation needed]}

From 1880 to 1898, Thatcher was the second assistant to Wilford Woodruff in the superintendency of the Young Men's Mutual Improvement Association (YMMIA).^{[citation needed]}

At the April 1896 General Conference of the church, Thatcher was dropped from the Quorum of the Twelve in consequence of his not being "in harmony" with the other leaders of the church about a proposed policy called "The Political Rule of the Church," commonly referred to as "the political Manifesto." This policy would have required that the general authorities of the church to obtain the approval of the First Presidency before seeking public office. This statement was signed by all the apostles at the time except Thatcher, who refused on grounds of conscience, citing the church's long-standing position on political neutrality. (Apostle Anthon Lund also did not sign the document due to his absence while presiding over the church's European Mission.)^[2]

However, Thatcher was not excommunicated from the church and retained his position in the leadership of the YMMIA.^{[citation needed]} Thatcher remained supportive of the church after being removed from the Quorum, testifying on many occasions of the divinity of the work and the divinity of the calling of its leaders.^{[citation needed]} Matthias F. Cowley replaced Thatcher in the Quorum of the Twelve. Thatcher held the priesthood office of apostle until his death.^{[citation needed]}

After being removed from the quorum, Thatcher testified in the Reed Smoot hearings held before the Senate Committee on Privileges and Elections.^[3] He was supportive of the church and its positions.^{[citation needed]}

Thatcher died at his home on August 22, 1909, in Logan, Utah.^[4]

• Moses Thatcher's Missionary Diaries Digital Collections, Harold B. Lee Library, Brigham Young University
• Grampa Bill's G.A. Pages: Moses Thatcher at the Wayback Machine (archived February 5, 2017)