Mendenhall joined the California-based tech giant in 2007. He was previously at Disney for 17 years, where he was executive vice-president of global marketing.
As first reported by PR Week US, published by Brand Republic owner Haymarket, it is widely expected that more executives will leave as its new chief executive Leo Apotheker shakes up the company.
Hewlett-Packard declined to comment.
Hewlett-Packard, which acquired Palm last year for approximately $1.2bn (£770m), is expected to launch its webOS tablet device in February.