The 22-year-old, who is eligible to face Nottingham Forest at The Valley on Saturday, fills the void left in the squad by Bradley Wright-Phillips' departure to Brentford on loan earlier this week.
"After losing Bradley Wright-Phillips I just felt we were short in the striker department," manager Chris Powell told the club's official website.
"Jonathan is a player we have kept an eye on this season in a number of games. I saw him when he played against us and he has an eye for a goal.
"He is a player full of potential and it is a chance for us to have a good look at him and hopefully he will come into the group and make an impact."
A product of Tottenham's youth academy, Obika has spent four loan spells with Yeovil and has scored for the Glovers against Charlton on two occasions.
Obika has also spent time on loan with Millwall, Crystal Palace, Swindon and Peterborough and he has also made two appearances for Tottenham's first team under Andre Villas-Boas this term.
He will compete for a place in Powell's starting line-up with the likes of Yann Kermorgant, Danny Haynes and Ricardo Fuller.
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- Chris Powell