Mickiewicz was born in Kraków, Poland, lived in Hamelin, Germany and currently resides in Vancouver, Canada. He created his first website at the age of 14, called Webmaster-Resources.com, which later became SitePoint. At 16, Mickiewicz traveled to Melbourne with his mother and met his soon to be business partner and co-founder, Mark Harbottle. At 16, Mickiewicz found himself closing $10,000 advertising deals between classes at high school. Mickiewicz barely finished high school and did not attend college.
In 2008, Mickiewicz spun off 99designs from SitePoint, which went on to raise $35 million in capital from Accel Ventures, Michael Dearing/Harrison Metal, Dave Goldberg (SurveyMonkey), Anthony Casalena, and Stewart Butterfield (Flickr). In June 2009, Mickiewicz and Harbottle launched Flippa.com, the largest marketplace for buying and selling websites in the world. In the fall of 2012, Mickiewicz co-founded DeveloperAuction.com which raised $2.7 million and was later renamed as Hired. The company later raised a $15 million Series-A round in March 2014. By December 2014, Hired was reportedly valued at $200m and had raised an additional $15m in capital in its Series B round.
Mickiewicz was named a 30 Under 30 Entrepreneur by Forbes and INC in 2011, a Smart Company 30 under 30 in 2012, and frequently speaks at conferences and seminars worldwide.