Later that same year, Kimball first heard Mormon missionaries preach; he was baptized 16 April 1832 and moved his family to Kirtland, Ohio--the headquarters of the new church. He subsequently went on eight missions between 1832 and 1841, including two to England (in 1837 he became the "First Mormon in the Old World"), participated in the Zion's Camp march of 1834, became a member of the First Quorum of Twelve Apostles in 1835, followed Joseph Smith to Missouri in 1838 and to Illinois in 1839, went west with the pioneers in 1846-47, crossing the plains three times. In 1847 he became First Counselor to Brigham Young, who had succeeded Smith as president of the church.
Kimball married forty-three wives and had sixty-five children and at least 300 grandchildren. In Utah he amassed land, cattle, and property, and was worth more than $100,000 at the time of his death. From 1848 until the time of his death twenty years later he participated fully in the political, economic, social, and cultural development of Mormondom's New Zion. He became chief justice of the unofficial state of Deseret in 1849, served in the territorial legislature from 1851 to 1858, generally presided over all temple work, assisted in colonizing the region, and fostered the area's economic independence.