Officers were called to the property, in Learmonth Crescent, shortly before 7pm on Saturday.
Residents in the area reported having seen police in the area for ‘a number of hours’ after the woman’s body was found.
They said there were two manned cordons in place on the street and at the property. There were also around six police vans in the area.
A Police Scotland spokesperson said: “Police Scotland are carrying out enquiries into the death of a 26-year-old woman following a call to an address in West Calder at around 6.40pm on Saturday, May 7.”
"A post mortem examination will be carried out in due course however the death is being treated as unexplained"