Blue badge holders and patients who must regularly attend appointments for long-term conditions will get free hospital parking under the plans being outlined on Friday.
All hospital trusts in England will also be expected to give free parking at specific times to parents with sick children staying overnight and staff on night shifts.
Trusts manage their own car parking arrangements and reinvest the profits into frontline care.
The Department of Health was not setting aside funding to reimburse trusts that may see their finances impacted under the Tory manifesto pledge.
But a department spokeswoman said "they will be supported" to ensure the policy does not affect care.
A study by the PA news agency earlier this month found one in three hospitals in England put up the cost of parking last year.
The research showed hospitals made more than £254million from parking in 2018/19, up 10% on the previous year.
Health Secretary Matt Hancock said: "One of the concerns mentioned regularly on the doorsteps was that vulnerable people, and staff working nights, have to pay for hospital car parking.
"Currently, the situation varies from hospital to hospital. Instead, from April, across the country those with the greatest need - such as disabled people, parents staying overnight with sick children in hospital, and NHS staff working night shifts - will no longer have to pay for parking."