He competed in the 2000 and 2004 Summer Olympics, coming in at fifth place in 2004 with Wayne Black. In mixed doubles, Ullyett won the 2002 Australian Open with Daniela Hantuchová. He reached the final of Wimbledon in 2002 with Hantuchová, and the semifinals there in 2003 and 2005 with Hantuchová and Liezel Huber, respectively.
He and Huber were also the runners-up at the 2005 Australian Open. Black, Ullyett’s compatriot and long-time doubles partner, retired at the end of 2005. He then played with Paul Hanley for two seasons, then with Jonas Björkman, who retired at the end of 2008, and finally with Brazilian Bruno Soares.
His father, Robert Ullyett, represented Rhodesia (now Zimbabwe) at cricket and field hockey. He made his final tennis appearance at the South African Open in February 2010 (partnering with Wesley Moodie) eighteen years after he first appeared there in 1992 competing in his first ATP Tour event. He had over 500 career wins.