The 32-year-old lock, who is currently playing in Japan with Suntory, made 13 appearances for the All Blacks between 2002 and 2004.
Having spent all of his career in New Zealand he joined Harlequins in 2004 before moving to the far east.
"Simon is just the type of player we are looking for to bolster our pack," said Scarlets chief executive Stuart Gallacher.
"Simon is an excellent lineout specialist and brings a wealth of experience with him into the squad."
Maling added: "I am really looking forward to joining the Llanelli Scarlets. It is great to be joining a traditionally strong region which has such a proud history.
"As a New Zealander I am looking forward to being back in a country where rugby is the number one sport."