Simester will take up his role in October.
He has been in his current role at Nestlé for two years. He was previously marketing manager for Nestlé's kit Kat brand.
Simester replaces Richard Hayes, who left in January after five years in the role. He will be based at Warburton's Bolton headquarters.
As Nestlé's head of chocolate, Simester headed up the company's £400m-turnover chocolate business, leading a 16-strong commercial team.
He was marketing manager for Kit Kit between 2004 and 2010.
His appointment at Warburtons comes as the business seeks to diversify from its core bread business and move into new categories such as snacks.
Warburtons is still on the hunt for a replacement for managing director Robert Higginson who also left the business earlier this year.
In the year to September 2011, profits at Warburtons declined 37% to £16.3m in 2011, which the baker attributed to increased competition and the cost of raw materials.
Earlier this month, Warburtons appointed WCRS to handle its £8m advertising account after a three-way shoot-out against VCCP and BMB.Follow @johnreynolds10