The 33-year-old reality TV star was asked by male model Michael Girgenti to allow Mason, three, to undergo the test, after he claimed they slept together while she and Scott, 30, were on a break in March 2009 but lab results have proved his allegations are false.
Kourtney, who has always denied Michael's allegations, told E! News: ''After three-and-a-half years of lies being spread by an individual I met briefly at a photo shoot, I am setting the record straight that Scott is Mason's father. While it saddens me to have to address these ridiculous lies - especially when the truth was never in doubt - this story must be put to rest.''
Scott and Kourtney also have a 13-month-old daughter Penelope.
This is not the first time the Kardashian family has been confronted by paternity allegations.
Kourtney's younger sister Khloe, 29, has had to regularly deny claims that their late father Robert Kardashian was not her biological father.
Their half-sister Kylie Jenner, 15, also recently hit back at reports that her father Bruce Jenner may not be her real father.
Recently, she shared her disgust in relation to the allegations with her fans on Twitter, writing: ''Yes, my father is my father and no my parents aren't getting a divorce. You guys can't believe any of these magazines. It's all bulls**t.
''And even though I don't let these stories get to my head. Imagine you at 15 & someone telling you your father isn't your father.
''EWWWW people disgust me. You're all pathetic.
''Wait. But you're ACTUALLY pathetic. Going after a 15-year-old and telling her father isn't her father. Like WHAT? Are you insane?
''This makes me so mad. And I'm not taking the time to write all this because this hurts me. I'm writing this for the other teens my age.''
Kai Whiston is back already with his second album of his own 'No World As Good As Mine', and this time he has the help of organic instruments.
Her debut album The Witching Hour is out soon.
Feet are mid-tour and promoting their debut album, and tonight they played Ramsgate Music Hall with support from local band Malpractice.
Famed for performing one of her own songs as her opening gambit on The X Factor, Lucy Spraggan rocked up at the Booking Hall as part of her UK and...
After nearly thirty years since his first solo record Mark Lanegan has just released one of his very best and there's not many artists who can claim...
Listen to their new single 'People Change'.
For the first, and almost certainly last, time Cambridge indie rockers Mallory Knox performed at The Booking Hall in Dover.
'Devour You' is a fantastic follow up to Starcrawler's debut album and represents a move on in terms of sound and, in part, direction.