It has hired Innocence to create the brand, which will be based on the 'crossed fingers' logo used by operator Camelot.
The appointment comes as Camelot prepares to launch a £12m ad campaign, starring Fay Ripley that uses the strapline 'Be lucky', (Marketing, 4 August).
The identity is being created as part of the National Lottery's aim to increase public awareness of the projects aided by the £16bn raised by ticket sales so far.
Other branding consultancies considered for the work included Roundel and Lambie-Nairn.
An NLPU spokeswoman said the good causes logo, which is being finalised, would have a serious feel to make it more appropriate for the organisations using it. Blue will be the only colour used, contrasting with the red, white and blue gaming identity.
Innocence is also developing brand guidelines for use of the mark.
The NLPU hopes the causes that receive lottery funding will use the brand identity on stationery and promotional literature.
The National Lottery recently streamlined its funding bodies to assist good causes applying for lottery funding. The Big Lottery Fund was created in June by the merger of the New Opportunities Fund and Community Fund.
It will hand out half the money for good causes from the Lottery.