Merrifield had passed George Brett (1980) for the longest streak in franchise history on Wednesday.
On Thursday, Merrifield had gone 0-for-5 through eight innings and the Royals were one strike away from a 6-4 win in the ninth. But Mitch Haniger hit a two-run triple off the glove of Royals center fielder Billy Hamilton to drive in two runs and the game went to extra innings.
After Daniel Vogelbach homered to put the Mariners ahead in the 10th inning, Merrifield then struck out to end the game. He had not gone hitless since Sept. 9.
"Out of my last nine outs, I feel like I've made six good swings on good pitches in the zone,'' Merrifield said. "I either hit it on the barrel at somebody or just missed it and hit it in the air. That's kind of what makes streaks like these so rare."
Merrifield's 31-game streak was the MLB's longest since Dan Uggla's 33-game streak in 2011.
On Twitter, Merrifield thanked the team's fans for supporting him during the streak, and the team through a 2-10 start, the worst in the majors.
"While it ended shorter than I would have liked and we haven't got off to the best start, stepping into the box and hearing your cheers last night is a moment I'll always remember," the tweet read. "Thank you for sharing that ride with me. Joe D is safe... for now," a reference to Yankees great Joe DiMaggio, who holds the major league record with a 56-game hitting streak in 1941.
Information from The Associated Press was used in this report.