The incident was reported at 3.15am on Monday, April 6, at a property on Cliff Parade.
A ladder, believed to have been used by the burglars, has been recovered from the garden.
South Wales Police said: “We understand that being a victim of burglary is traumatic, and we are working hard to catch the people responsible.
“While our investigation and patrols are on-going, please take extra steps to protect your property.
“Please be vigilant to anyone acting suspiciously in the #Penarth area.”
Officers are appealing for anyone with CCTV and dashcam footage, or other information to please contact police.
They are particularly interested in footage from Plymouth Road, where two suspects were seen around 1.25am carrying a ladder.
This was shortly before the burglary took place.
Witnesses or anyone with relevant footage are encouraged to contact police online at www.south-wales.police.uk/ro/report, by calling 101, or through Crimestoppers anonymously on 0800 555 111.
In an emergency, the public should always call 999.
