Japan's most decorated club claimed the title from the most unpromising of circumstances having gone 1-0 down, 2-0 on aggregate, at Urawa Reds' Saitama Stadium in the second leg of the championship final on Saturday.
A brace from striker Mu Kanazaki, the second a 79th minute penalty, silenced the 60,000 crowd and gave Kashima their first title for seven years to complete the line-up for the FIFA's showpiece club competition.
Real Madrid, South Korea's Jeonbuk Motors, Colombia's Atletico Nacional, Club America of Mexico and South Africa's Mamelodi Sundowns complete the line-up for the Dec. 8-18 tournament.
There is at least no great travelling involved for Masatada Ishii's squad as their match against Oceania Champions League winners Auckland takes place in Yokohama, one of two host cities with Osaka.
Victory over the New Zealanders in the playoff would put Kashima into the tournament proper with the prospect of facing European champions Real.
"We are not looking too far ahead at the Club World Cup and will be taking it one match at a time and analyse our opponents and think about how we need to play," Ishii said on Saturday.
(Reporting by Nick Mulvenney in Sydney, editing by Peter Rutherford)
