The woman entered her property in Broxburn sometime between 8.10pm and 8.35pm yesterday.
She saw a male climbing over the fence in the back garden before running off.
She then contacted police after finding laptops and jewellery had been stolen from inside.
The total value of the stolen items is around £7500.
Officers are now urging anyone who can assist with their enquiries to come forward.
The suspect is described as white, 15-20-years-old, between 5ft 10ins and 6ft tall with a medium build and thick dark hair.
He was wearing a red top with greenish yellow stripes down the sleeves and was carrying an orange coloured plastic bag.
A police spokesman said: “The victim has been left extremely upset after her home was entered and her possessions stolen.
“Anyone who remembers seeing any suspicious activity in the area yesterday evening, or who can help identify the suspect is asked to contact police immediately.”