The 29 year-old Icelandic midfielder has been a long term target for Evans, as he explained to the clubs official website after getting his man.
''Kari is without doubt an outstanding talent and I am delighted we have brought him to Rotherham United. He is a player who I first spotted at Plymouth Argyle and I followed his performances last season at Aberdeen with real interest.
"I have signed the lad to play in midfield but he has also represented his country at Centre Back and Full Back; his versatility is a major asset.
''The lad is technically outstanding, he is very creative in the attacking third, his all round range of passing is top class. When you add that to his physique, defensive awareness and work rate there is no doubt this is a major signing for all of us, the staff, players and of course our supporters who will love him." added Steve.
''I have clocked up many hours and miles in getting this deal done but it will be worth it. My thanks go to my Chairman Tony Stewart and the Directors for all their support."