Josh Duggar has been convicted of downloading and possessing child pornography.
He faces up to 20 years in prison after the jury in Fayetteville, Arkansas, found him guilty on both counts at a hearing on Thursday.
Duggar is one of the former stars of 19 Kids and Counting, a reality show about the devout Christian Duggar family.
He also faces up to $500,000 in fines.
Prosecutor Clay Fowlkes, speaking after the verdict, said, "Regardless of wealth, social status, or fame, our office will continue to seek out all individuals who seek to abuse children and victimize them through the downloading, possession, and sharing of child pornography."
Duggar was immediately taken into custody following Thursday's hearing and is due to be sentenced in four months.
He plans to appeal.
His defence attorney Justin Gelfand said, "We respect the jury's verdict and we look forward to continuing this fight on appeal."
19 Kids and Counting was a hit reality TV show on the TLC network until 2015 when it was cancelled after it emerged that Duggar had molested four of his sisters.
He later went into rehab for a porn addiction and admitted to cheating on his wife Anna Duggar.
She has stayed with him and gave birth to their seventh child in November, just weeks before her husband's trial started.
