The tournament, which will now be named the Daily Mirror Grand Slam of Darts, brings together the world's best players including 15-time world champion Phil Taylor at the 1,200-seater Wolverhampton Civic Hall.
The estimated £450,000 deal, brokered by Mean Broadcast, gives the Mirror naming rights, full branding at the event and on tickets as well as broadcast advertising opportunities.
The Mirror will publish editorial between now and the end of the event, which began with an eight-page special pull-out last week and will continue with a run-down of players' profiles.
Richard Wallace, editor of the Daily Mirror, said: "We're delighted to be involved as sponsors of this Grand Slam event as it is the only tournament where you will see the greatest darts players go head-to-head for a six-figure jackpot.
"This is an ideal partnership for the Mirror, and our readers, and once again confirms our commitment and long-term investment in sport."