In 1905, when Kristiansen was 14, he began working as an apprentice to his brother. In 1911 he left Denmark and went to work in carpentry for five years in Germany. Kristiansenbought the Billund Woodworking and Carpentry Shop with money he had saved, and made profitable sales over the years. He married the daughter of a Norwegian cheese-maker, Kirstine Sorensen. Together, they had four children: Johannes, Karl, Godtfred and Gerhardt.

In 1924, Karl and Godtfred began to tinker with wood shavings. A fire broke out consequently. Both the factory and their home burned down.

During the early 1930s, Ole’s business fell into the Great Depression as its peak rose in Denmark. Ole was able to make items such as Christmas tree stands and toys. His business was becoming slow. The primary income, which was from sales of ladders and ironing boards, was shrinking in demand. Eventually, Ole had to dismiss his last worker, and his wife died. Ole decided to officially found an unnamed company (later to become LEGO) in 1932.

Kristiansen wanted a name for the group. In 1934, he launched a competition to name the company. The prize was a bottle of his own homemade wine. He created his own name, Lego, and he won it himself. Lego is a shortened form of the Danish words Leg godt, meaning “play well”, and the company grew to become The Lego Group.

Kristiansen’s company expanded throughout the 1940s and 1950s. In 1947, he purchased a self-moulding machine and began production of plastic toys. His son Godtfred became managing director and later CEO. All of Ole’s sons assisted in his company, and in 1958 the LEGO Brick patent was created.

On 11 March 1958, Kristiansen experienced a heart attack and died at the age of 66, and his third son Godtfred promptly took over the company until his death in 1995.