The kiss happens in the seventh and final book in author J.K. Rowling's series and Watson told a news conference on Thursday promoting the sixth film "Harry Potter and the Half-Blood Prince" that the scene was filmed two weeks ago.
"This is 10 years worth of tension and hormones and chemistry and everything in one moment. We had to ace it," said Watson. "Kissing is awkward, kissing is always awkward."
The final book, "Harry Potter and the Deathly Hallows," is being split into two films and it remains unknown which of the final two movies contains the kiss.
"It's not something we were really looking forward to," said 20-year-old Grint. "It was quite a strange thing to have to think about doing."
But it doesn't seem strange for fans because a lot appear to be excited about it. In a poll conducted by online ticket seller Fandango.com , 59 percent of fans said the on-screen kiss they most want to see is between Hermione and Ron.
Only 40 percent said they can't wait to see the peck in "Half-Blood Prince" between Potter, played by Daniel Radcliffe, and Ginny Weasley, Ron's sister in the film who is played by Bonnie Wright.
"I saw the film again a couple of nights ago at the premiere and ... my God, my lips are like the lips of a horse, kind of distending independently away from my face and trying to encompass the lower half of hers," Radcliffe, 19, said.
"So I apologize for that," he said.
"Harry Potter and the Half-Blood Prince" hits theaters on July 15, while part one of "Harry Potter and the Deathly Hallows" is due out in late 2010 and part two is planned for release in summer 2011.
Sources: Reuters