Paulina Miller, 14, was last seen at 7pm on Wednesday (April 5) when she boarded a southbound Bakerloo line train on the London Underground at Piccadilly Circus station.
Paulina is described as white, around 5ft 4in tall, of slim build with blue eyes and shoulder length blonde hair.
It is not known what the teenager may now be wearing.
A spokesman for the Metropolitan Police Service said on Sunday (April 9) that officers trying to locate Paulina were becoming “increasingly concerned for her welfare”.
Anyone who has seen Paulina or who has information that could help the force find her is urged to call officers at Ealing police station on 101, or Missing People on 116000.
Alternatively, any sightings of the teen can be reported via Twitter at @MetCC.