Dimitrios Liakos, 70, disappeared on the morning of Tuesday, October 6, from the village of Serbia in Kozani.
The elderly suffer from dementia and face other health problems.
He is 1.75 tall, has brown eyes and is bald with some white hair on the side.
When he disappeared, he was wearing a white jacket, a sweater, blue jeans and sneakers.
For his disappearance Silver Alert has been activated.