A pig's head was thrown through the window of a home in Bonython, Tuggeranong, on Saturday night, with another head discovered in nearby lane.
Around 10pm, a resident of the house called police to report a pig's head had landed on the kitchen bench after it crashed through a window, breaking the glass.
Police on the scene on Saturday also found a second pig's head discarded in a nearby laneway.
Police media say two plastic bags were also found on the scene and have been seized for forensic analysis.
ACT Policing say they are puzzled by pork projectile and have labeled the incident "bizarre".
Bonython resident Eileen Rodman, who was unaware of the incident, has planted large cactus plants around lights on her fence in order to stop vandals breaking them.
She told The Canberra Times she felt very safe in the suburb but had eggs thrown at her windows in December last year.
Other Bonython residents also had eggs thrown at their windows near the end of last year, but suspected it was the work of young people bored on school holidays.
Police are appealing for any witnesses and asking anyone with knowledge of the incident to report it to Crime Stoppers on 1800 333 000.