The charity has shortlisted three agencies that will pitch for the business this week.
The incumbent, WWAV Rapp Collins, which currently handles the NSPCC's low-value donor direct marketing, is understood to be involved in the process. The pitch is being handled by Allan Freeman at the intermediary Freestyle Marketing.
Kitcatt Nohr Alexander Shaw, the incumbent agency on the NSPCC's high-value donor direct marketing, has declined to pitch.
The successful agency will be charged with creating the children's charity's first major integrated below-the-line campaign for legacy donations.
The campaign will seek to increase the charity's legacy income, which currently accounts for just 20 per cent of the NSPCC's total revenue.
A spokeswoman for the NSPCC confirmed that a pitch was taking place.