Louis Richards, 25, was last seen in Blackburn town centre but is believed to have travelled straight to Preston on Friday evening.
Police say they are becoming "increasingly concerned" for his welfare and are appealing to the public for help finding him.
Louis is described as having long brown wavy hair (often tied up on top of his head), brown eyes and a beard.
He is very slim and approximately 6ft 2in tall. Officers say his clothing is unknown at this time.
A police spokesman said: "We are becoming increasingly concerned about his welfare and are appealing for your help to find Louis.
"If you have seen him or have any information, please call us on 101 quoting reference LC-20210924-1484.
"Please share this post and thanks for your help."
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