He was sentenced to 15 years of hard labour after a show trial, and fell into a coma during his detention for reasons that remain unexplained.
North Korea said he suffered an allergic reaction to food, but the Warmbier family said he had been tortured and abused.
He died in the United States in June 2017, days after the North Korean regime authorised a medical evacuation.
Fred Warmbier and his wife Cindy have praised President Donald Trump for securing their son’s return and criticised former president Barack Obama for failing to bring him back sooner.
The Warmbiers were singled out by Mr Trump during his State of the Union address last week.
“You are powerful witnesses to a menace that threatens our world, and your strength inspires truly us all,” Mr Trump told them as they sat in the audience with their younger children Austin and Greta.
“Tonight, we pledge to honour Otto's memory with total American resolve.”
