Paula Palmer said jewellery given to her by husband Dennis on their wedding day was among the items stolen from the house in Barnett Road, Brighton.
"It's devastating to think people can do that," she said. "I am numb."
Mrs Palmer said she believed the thieves knew where the occupants of the house were when the break-in happened on Friday evening.
"We were waiting outside for the hearse to come for a good 20 minutes," she said.
"It doesn't take long for people to know what you are doing."
She said she knew something was wrong when she returned home with a group of people.
"By the time I reached the top of the stairs I could see the devastation in the main bedroom," she said.
"My husband's jewellery box was broken open, the wardrobe doors were open and all drawers tipped out.
"I was numb anyway from burying my husband - but to come back, to that I was speechless."
The stolen jewellery included gold earrings, necklaces and bracelets.
The thieves also took the keys to Mrs Palmer's grey Kia Ce'ed car, registration BJ09 YBK, and drove it away from the front of the house.
"It is quite brazen and quite unusual for people to walk out of the front door, get in the car and drive off," said Det Con Richard Valder-Davies.
"This is an awful crime. This lady was at her husband's funeral. It doesn't get much worse than that."
Sussex Police have appealed to anyone with information, or who is offered jewellery in suspicious circumstances, to come forward.

North Wales Police added that from those tests, 60 arrests were made.
It follows a report earlier in December which said motorists are more likely to be tested for drink driving in north Wales than anywhere else in the UK.
Det Ch Con Gareth Pritchard warned motorists not to be tempted to drink and drive.
He said: "Officers will continue to carry out breath tests across north Wales as part of our campaign to reduce deaths on the roads."
Thieves ransacked a widow's home and stole jewellery, cash and her car while she was at her husband's funeral.
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More than 13,000 people have been tested for drink and drug driving in north Wales the run up to Christmas, police said.