The attempted burglaries are believed to have happened in the Cae Canol and Rhos Du areas.
South Wales Police said a “suspicious unknown individual” was captured on CCTV trying door handles at night.
Officers are now working to identify the person.
A spokesperson for South Wales Police said: “We are investigating reports of three attempt burglaries in the Cae Canol and Rhos Ddu areas of Penarth.
“A suspicious unknown individual has been seen on CCTV at night trying door handles.
“While we continue to try to identify this person, please ensure your properties are secure, keep keys away from doors and windows and contact police immediately on 999 if anyone is seen acting suspiciously”.
Members of the public are being urged to make sure their properties are secure.
Anyone who sees anyone acting suspiciously is being told to call 999.
Enquiries remain ongoing.
