Gardai are investigating the desecration of plots and headstones at St Joseph's Cemetery in Cork.
Headstones were knocked over while plaques and marble shields on some graves were ripped up and smashed.
The Woods family, which has three generations of relatives buried in a St Joseph's plot, described the incident as "cruel and heartless".
"How could anyone with any piece of humanity do this to the dead," Eileen Woods from Crosshaven asked. "It is frightening to think there are people out there who are capable of doing a heartless act like this."
Gardai have appealed for anyone who may have spotted suspicious activity to contact them.