The 31-year-old follows former Royals Stephen Hunt and Kevin Doyle to Molineux with a view to making a permanent move in the summer.
The Latvia international has plenty of experience of Championship football following spells with Reading and QPR, and Wolves boss Dean Saunders is confident he can help the club in their bid to avoid relegation.
"I am delighted we have brought Kaspars in," Saunders told the official Wolves website.
"He has been with teams who have been promoted from the Championship over the last two years and is 31 which is a good age for a central defender.
"I think he can help take us where we want to go. He is strong, brave and no-nonsense who will put his head in which is what we need.
"He also has a good character and is a winner, and that can only help the group. He is an experienced player who has played in the Premier League this season and also played for his country last Wednesday night.
"This is a start for me of what I am trying to build here."
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