BT Retail director of comms Alison Jeremy starts at the children's charity on 8 November.
Grounds' new role was announced in November last year, with the charity quickly promoting deputy director of comms Keith Bradbrook to fill his role.
However, the organisation now claims this was only an interim measure, with Jeremy taking the post on a permanent basis.
Bradbrook will continue as deputy director of comms, having worked at the charity for 12 years.
Jeremy joined BT last November, before which she was director of comms at BBC Worldwide, having also worked at Firefly Communications as group associate director.
A BT spokeswoman said: 'Alison has done a great job and we wish her all the best in the future. There is no news on her replacement at this stage.'
Bradbrook replaced highprofile comms expert Grounds, who took up a wider management position within the charity. Grounds stepped into a new role as director of the Child Protection Consultancy last November. This separate unit is responsible for the charity's external relations with stakeholders.
The news comes as the NSPCC has announced it is supporting new British film The Kid, which tells the story of a young man's poverty-stricken and violent upbringing. The charity's brand ambassador Kylie Minogue attended the premiere on 15 September in Leicester Square.
In March, the NSPCC called in digital specialist Hot Cherry to run a social media campaign promoting its ChildLine service.
The charity is keen to ensure that teenagers are aware they can contact ChildLine online.