Snow's Baptist parents welcomed a variety of religious believers into their home. In 1828, Snow and her parents joined Alexander Campbell’s Christian restorationist movement, the Disciples of Christ. When Joseph Smith, Jr., the Latter Day Saint prophet, took up residence in Hiram, Ohio, four miles from the Snow farm in 1831, the Snow family took a strong interest in the new religious movement. Eliza's mother and sister joined the Latter Day Saint Church early on; several years later, in 1835, Eliza was baptized and moved to Kirtland, Ohio, which was at the time the headquarters of the Church. Upon her arrival, Eliza donated her inheritance, a large sum of money, toward the building of the Church's Kirtland Temple. In appreciation, the building committee provided her with the title to “a very valuable [lot]-situated near the Temple, with a fruit tree-an excellent spring of water, and house that accommodated two families.” Here Eliza taught school for Joseph Smith's family and was influential in interesting her younger brother Lorenzo Snow in the young Church. Lorenzo later became fifth President of The Church of Jesus Christ of Latter-day Saints.

Snow moved west with her family and the body of the Church, first to Adam-ondi-Ahman, a short-lived LDS settlement in Missouri, and then to Nauvoo, Illinois. In Nauvoo, Snow again made her living as a school teacher. It is alleged she secretly wed Joseph Smith, on 29 June 1842, as a plural wife. Derr claimed that Eliza wrote fondly of Joseph “my beloved husband, the choice of my heart and the crown of my life”. However, Snow organized a petition in Summer 1842, with a thousand female signatures, denying Smith was connected with polygamy. Furthermore, as Secretary of the Ladies' Relief Society she organized the publishing of a certificate in October 1842 denouncing polygamy and denying Smith as its creator or participant.

Snow married Brigham Young as a plural wife. She traveled west across the plains and arrived in the Salt Lake Valley on 2 October 1847. There, childless Eliza became a prominent member of Young's family, moving into an upper bedroom in Young's Salt Lake City residence, the Lion House.

Snow served as the first secretary of the LDS women's Nauvoo Female Relief Society in 1842 under the presidency of Emma Smith. Called by Young in 1866 to help bishops organize Relief Societies in local wards and to "instruct the sisters," Eliza traveled throughout Utah Territory encouraging women to attend meetings, sustain priesthood leaders, and support Young's economic programs.

Snow’s presidency emphasized spirituality and self-sufficiency. The Relief Society sent women to medical school, trained nurses, opened the Deseret Hospital, operated cooperative stores, promoted silk manufacture, saved wheat, and built granaries. In 1872 Snow provided assistance and advice to Louisa L. Greene in the creation of a woman's publication loosely affiliated with the Relief Society—the Woman's Exponent. Snow's responsibilities also extended to young women and children within the Church. She was a primary organizer for the Young Ladies' Mutual Improvement Association in 1870 and assisted Aurelia Spencer Rogers in establishing the Primary Association in 1878.

Snow served as president of the Relief Society until her death in 1887. By 1888, the Relief Society had more than 22,000 members in 400 local wards and branches.

Snow died on December 5, 1887, in Salt Lake City, and was buried in Brigham Young's family cemetery.

Eliza R. Snow wrote poetry from a young age, one time even writing school lessons in rhyme. Between 1826 and 1832 she published more than 20 poems in local newspapers, including the Ravenna, Ohio Western Courier and the Ohio Star, using various pen names. A number of Snow's poems were set to music and have become important LDS hymns, some of which appear in the current edition of the LDS Hymnal. One of her hymns, "Great is the Lord", was published in the first Latter-day Saint Hymnbook in 1835, the year of her baptism. In Nauvoo, Eliza R. Snow gained unique distinction as a Mormon poet featured in local newspapers, and she was later called "Zion's Poetess." She continued to write poems as she crossed the plains, documenting the pioneer trail and life in Utah. The first of her two volumes of Poems, Religious, Historical, and Political appeared in 1856, followed by the second in 1877. Some of her poems include:

• "How Great the Wisdom and the Love" ( text)
• "Invocation, or the Eternal Father and Mother" ("Oh, My Father") ( text)
• "Be Not Discouraged" ( text)
• "My First View of a Western Prairie" ( text)
• "Mental Gas" ( text)
• "Think not When You Gather to Zion Your Troubles and Trials are Through"
• "O Awake! My Slumbering Minstrel"
• "Truth Reflects upon Our Senses"

One of her best-known poems, "Invocation, or the Eternal Father and Mother," was written soon after the death of her father, just over a year after the death of Joseph Smith, who taught concepts of the eternal family (Eliza R. Snow, "My Father in Heaven", Times and Seasons 6 [15 November 1845]; see Derr, below). This poem, renamed "O My Father", is included in the current LDS Hymnal.

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• Snow, Eliza R. "Biography and Family Record of Lorenzo Snow, One of the Twelve Apostles of the Church of Jesus Christ of Latter-day Saints." Salt Lake City, Deseret News, 1884.

--Reprinted 1999, Church of Jesus Christ of Latter-day Saints. Salt Lake City.

• Snow, Eliza R. Poems: Religious, Historical and Political. 2 vols. (Liverpool: F.D. Richards, 1856).