Mortensen was born in East Malvern, Melbourne in 1939 to a Danish migrant father and an Australian mother. Growing up in a household rich in creativity and culture, his early experiences laid the foundation for his future in the world of art. Pursuing his passion, he embarked on a journey of artistic education at Prahran Technical College, where he was mentored by the skilled sculptor Lenton Parr. This pivotal period not only honed his skills but also ignited a profound artistic vision within Mortensen, setting him on the path to becoming a renowned sculptor.

Kevin always felt a profound and deep connection to Gippsland – a region he cherished as a tranquil haven enveloped by nature's beauty. This strong bond with the area stemmed from generations of family roots intricately entwined with the locale, leading him to settle and build his life in Venus Bay since the year 1985. The peaceful surroundings and the sense of belonging he found in this coastal paradise influenced his art in profound ways, reflecting the harmony and serenity that defined his daily life and creative inspiration.

During the 1970s and 80s, Mortensen devoted his energy to sharing his artistic insights as a lecturer at RMIT. His creative pursuits garnered acclaim through high-profile presentations at prestigious gatherings like the Mildura Sculpture Triennials and the Biennale of Sydney. These opportunities played a significant role in cementing his stature as a prominent presence in the Australian art community. A pivotal moment in his career was being chosen to represent Australia at the esteemed 1980 Venice Biennale, an esteemed event he shared with fellow artists Tony Coleing and Mike Parr. His artistic influence continued to shine at subsequent editions of the Australian Sculpture Triennial in 1981, 1984, and 1989, further enriching his legacy in the artistic realm.

Mortensen’s diverse artistic practice spans across a rich tapestry of mediums including drawing, painting, sculpture, installation, and performance. Over the course of his career, he has delved deeply into themes inspired by the ocean, landscapes, and a myriad of animal forms, often centering his exploration on the enigmatic world of birds. The enduring presence of the birdman motif stands out prominently in Mortensen’s body of work, a symbol directly influenced by his engagement with the age-old Danish tradition of fugleskyding, centered around bird hunting. This cultural heritage has seamlessly woven its way into the very fabric of Mortensen’s creative persona, shaping a distinctive and profound aspect of his artistic expression.