Nikara has long been viewed as one of the quickest young drivers in Finland, and was part of the inaugural Pirelli Star Driver scheme in 2009.
He has mostly driven Group N cars since. Catalunya will mark his first WRC round in a World Rally Car, and his debut with Prodrive.
The firm's business development director Richard Taylor said he was excited at the Finn's arrival.
"Prodrive are delighted to have Jarkko in the team for Rally Spain," said Taylor.
"He has shown excellent pace on a range of events in the last couple of years and was particularly impressive in winning Group N in Finland this year where his stage times were often better than drivers with more modern and more powerful machinery.
"Of course this will be his first time in a Mini WRC car, however we expect him to set some strong stage times and we think he may surprise a few people."