Chicago-based Mikhalevsky was number five on the dairy giant's executive ladder as managing director of Global Ingredients and Foodservice.
Fonterra said he had accepted a senior job with California Dairies, one of the biggest dairy operators in the U.S., which recently joined Fonterra's online global auction platform Global Dairy Trade.
He will leave at the end of the year.
Mikhalevsky had been with New Zealand's biggest company for five years.
New Fonterra chief executive Theo Spierings said Mikhalevsky had forged strong customer partnerships while leading the premium ingredients business.
Director of global formulated foods Alex Turnbull will be acting managing director of Global Ingredients and Foodservice while a recruitment process gets under way.
From the November 16, 2011, Prepared Foods' Daily News.