Wuya Kamara was last seen in the East Hill area of the town at around 3.10pm yesterday (November 15).
The 15-year-old is described by police as being around 5ft 3in, of slim build and currently has straight orange hair.
She was last seen wearing a black jacket with black leggings and trainers.
Wuya has connections to London, Tonbridge and Hastings.
Officers are concerned for her welfare.
A spokesperson for Kent Police said: “Anyone with critical information about her whereabouts is urged to call 999 quoting reference 15-1005.
“Any other information can be provided by calling 101.”
