Harrison Rock was last seen at 6pm in Middlesbrough but has not been seen since.
Officers are now increasingly concerned for his welfare.
When Harrison went missing he was wearing a blue tracksuit and grey trainers.
A Cleveland Police spokesperson said: “15-year-old Harrison Rock travelled to Middlesbrough from Halifax in West Yorkshire yesterday.
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“He was last seen at 6pm in Middlesbrough yesterday but hasn’t been seen since. Officers are concerned for his welfare.
“He was wearing a blue tracksuit and grey trainers.
“Anyone with information on his whereabouts is asked to call 101 quoting reference 236056.”
