Kendall, 19, first appeared on Keeping Up With The Kardashians when she was just 11-years-old and has gone on to become a successful fashion model.
But the teen confessed that growing up around Kourtney, 35, Kim, 34, Khloe, 30 and 27-year-old Rob made her mature faster.
Writing in her first column for the Wall Street Journal, Kendall said: "I feel like a grew up too fast a long time ago.
"Having older siblings, you grow up around adults, so you mature more quickly."
Kendall, who has walked the runway for Marc Jacobs and was recently announced as the face of Estee Lauder, insisted her strong work ethic comes from being a part of the ambitious family.
She continued: "I saw my sisters and parents working every day so I was pretty much bought up to be a workaholic.
"My sister Khloe always says to me and my younger sister Kylie, 'You have your whole life to be an adult but only so long to be a kid', and we get it."
And Kendall said she does try to remember she is only 19, adding: "In the right situations, I try to be as immature as I can sometimes – react to things as if I were 12.
"You can't take things too seriously. But I'm scared to be 20 – it's the first step out of being a teenager."