The month-long drive will build on the relaunch of the building society's investment services earlier this year and includes in-branch activity, direct mail and press advertising.
The campaign, created by direct agency TDA, will target existing customers.
It aims to demystify the concept of financial investment by removing traditional barriers for consumers such as fear of losing money and a sense of elitism.
Press ads will run in national newspapers including The Times and Daily Mail.
The work will highlight that Nationwide customers can invest from as little as £20, use a lump sum or make regular payments.
If you have an opinion on this or any other issue raised on Brand Republic, join the debate in the .