Tinker and Flash had cancerous tips, which the RSPCA said sun cream could have helped prevent.
The two domestic shorthair crossbreeds, who were taken to the charity's centre in Bryn-y-Maen, were more at risk to sun damage due to the pigment of their skin and less fur on their ears.
The charity said both were recovering well at the centre, near Colwyn Bay.
Tinker, who is about four, is ready for rehoming after her owner died. Flash is about nine and is still recovering.
Animal centre manager Victoria Williams said: "It is such a shame that Tinker and Flash have lost part of their ears - but they are both adorable cats and will make lovely pets."
The RSPCA has warned people to be aware of the damage the sun can do to cats over the summer months.
Two white cats in Conwy county had to have parts of their ears removed due to sun damage.