Megan Smith, 13, was last seen at around 4.30pm on Thursday in Wakefield Bus Station.
She is white, around 5ft tall and has medium-length brown hair.
The last time she was seen, she was wearing blue jeans and a black jacket.
Police said the 13-year-old, who is from Wakefield, has contacts in Barnsley.
Det Insp Dan Tillett, from Wakefield CID, said,”I would appeal to anyone who has seen or heard from Megan since yesterday afternoon, or who knows where she is now to get in touch.
“It is out of character for Megan to go missing and we are concerned for her safety.
“ I would appeal directly to Megan to get in touch with police to let us know that she is OK. Enquiries are ongoing.”
Anyone with information should contact Wakefield CID via 101, quoting log 1856 of July 7.