Raymond Jessop, 38, was also ordered to pay an $8,000 fine, KSTU-TV, Salt Lake City, reported. A jury in Eldorado, Texas, sentenced him after deliberating five hours.
Jessup and 11 other men were charged after a raid last year on the Yearning for Zion Ranch, operated by the Fundamentalist Church of Jesus Christ of Latter-Day Saints. More than 400 children were seized in the raid, although courts later ordered them returned to their mothers.
Investigators determined some men had married under-age girls. Jessup's wife was 15 when they married and 16 when she had a child.
"This is a case about the flesh and blood of a victim," Assistant Texas Attorney General Eric Nichols told the jury as he showed a picture of Jessop and his wife.
Defense lawyers used photographs of children and families to suggest those involved in polygamous relationships at the ranch are happy with it.