Police will look through CCTV footage in the hope of tracking down the vandal who smashed several windows at the Lindt Cafe in Martin Place.
At least five rocks were hurled through the windows of the cafe, which was the scene of a deadly siege in December, in the early hours of Wednesday.
Witnesses say a man was loitering at the scene at the time of the attack.
"We believe a man in his 40s with facial hair and tanned skin may be able to assist with inquiries," a NSW police spokeswoman said.
An inquest into the siege, which claimed the life of hostages Katrina Dawson and Tori Johnson, as well as gunman Man Monis, is set to continue in Sydney on Wednesday.
