Weston will have responsibility for developing and co-ordinating the brand and strategy for M&S food business.
He will report in to M&S marketing director Steve Sharp, whose role remains unchanged.
Weston was head of strategy and international development at John Lewis.
M&S has also appointed Damian Guha, former managing director of Mars’ Czech Republic and Slovakia business as director for its home business.
Guha will report to Marks & Spencer general merchandise director Kate Bostock.
The appointments follow several senior hires in recent weeks to deliver the vision CEO Marc Bolland outlined in November to strengthen the M&S brand and leverage its heritage.