Francisco Parente, aged 22, was last seen in Western Road, Crookes, on Sunday, June 16, at about 9pm.
His mum Ana Pires today revealed that she last spoke to him that night and everything seemed normal.
Today she desperately urged him to come forward.
Ana said: “He seemed fine when I spoke to him and nothing seemed out of the ordinary.
“He has not gone missing before and this is very out of character for him.
“I am beyond worried. I just want him to come forward and make contact to say that he is alright.”
Francisco is originally from Portugal and has been studying at the University of Sheffield for about three years.
Police believe he may have a tent, rucksack and sleeping bag with him like the ones pictured.
Ana said: “One of his friends said he might be in the Peak District and I think that is possible. He used to be in the scouts when he was younger.”
He is thought to be wearing a blue anorak, blue jeans and brown leather slip on shoes.
South Yorkshire Police also issued a re-appeal for information about his whereabouts today and in a statement said: “Have you seen Francisco?
“If you can help please call 101 quoting incident number 895 if 18 June 2019.”