The OAP's granddaughter was pictured on Twitter holding a sign saying 'Free my Grandpa'.
Her roommate tweeted to say he had been held at the airport with "other Muslim people."
But an emotional video posted later shows the grandfather waving as he was released and allowed into the country.
The granddaughter's roommate Kari Vescio tweeted a video of him walking free and added: "He is free! After 9+ hours of being detained. Thank you everyone for protesting with us."
It is not known which country the 80-year-old had been travelling from.
The new US President announced on Friday that all refugees would be banned from entering America.
Trump also banned nationals from seven mainly Muslim countries from entering the US.