Naomi Gallagher, 14, of Kilmarnock was last seen on Saturday, December 31, at her grandmother's house in Scott Court, Helensburgh at around 4pm, as reported in last night's Evening Times.
Naomi, who is approximately 5ft 4in tall, with brown eyes and shoulder-length black hair with a side parting, was wearing a purple and grey reversible hooded jacket, a leopard-print top, black leggings and a pair of black UGG-style boots.
Her mother, Karen McMonagle, has appealed for her daughter to get in touch.
"Originally, with it being Hogmanay and Naomi being Naomi, I wasn't too concerned but it's becoming a worry," she said.
"Unfortunately she has been known to come back late or stay out, but she always came back and has never stayed away so long.
"I just want her to let us know she is OK," added Mrs McMonagle, 33.
Naomi's stepfather Paul McMonagle, 42, said: "Get in touch with someone. Get in contact with gran, us, the police, anybody. Phone, text or Facebook, just please let us know you're OK," he said.
Andy Hutton, Chief Inspector at Dumbarton Police Office, said: "We believe that, although Naomi was last seen on Hogmanay, she has been in touch with friends since then, and I would ask those she may have been in contact with to call and give us any information they have."