The £1.3bn drive will increase the number of nurses, therapists, psychiatrists and other mental health professionals to treat an extra one million people and provide services seven days a week.
But the Royal College of Nursing has said the timeframe appears "not to add up" because the nurses would have to start training next month to be ready in time.
Retaining staff, and encouraging some of the 4,000 psychiatrists and 30,000 mental health nurses not substantively employed by the NHS to return is key to the plan.
Mr Hunt said his goal was "ambitious" and meant "supporting those already in the profession to stay and giving incentives to those considering a career in mental health".
He told Sky News is was important to do more because "we still have too many tragedies, too many young lives cut short because we're not helping people quickly enough".