Nicholls-Magielsen has been appointed to the new role of director of new concepts at KFC.
She will be responsible for marketing new product developments across its breakfast and beverage range.
Nicholls-Magielsen, who is leaving Pizza Hut at the end of the month, will report to KFC vice president of marketing, Jennelle Tilling.
She has been marketing director, restaurants, at Pizza Hut UK since July 2007, a role in which she oversaw the launch of a new pasta menu and Tuscani pizzas.
Prior to her time at Pizza Hut, she worked at Proctor & Gamble for eight years. The two food chains are owned by US restaurant giant Yum!.