A red and white Trek mountain bike was taken from an enclosed courtyard in Piette Road some time between midday on 17 September and 20:00 on 20 September.
Guernsey Police is keen to speak with anyone has seen a bicycle matching this description or who witnessed its theft.
You can contact the Force on 725111 or, alternatively, call Crimestoppers anonymously on 0800 555 111, quoting OC2000006500.