The Terrorism Investigation Division (TID) arrested the accused in the north along with posters commemorating Prabakaran's birthday yesterday, police spokesman Ajith Rohana said.
A laptop and a data storage device which contained such materials were also seized from him.
"We can't allow commemoration of a terrorist leader in public," Rohana said.
Sri Lanka government troops and the LTTE were locked in a nearly-three decade bloody war that ended in 2009 with the defeat of the Tamil Tigers following the death of its chief Prabhakaran.