The initiative is central to the Assembly's plans in developing the country's electronic economy.
The agency will be responsible for creating a £2m 18-month integrated campaign. As well as targeting consumers, it will be aimed at businesses, voluntary organisations, charities and public sector bodies across Wales.
Broadband Wales is leading the search. The body was set up by the Welsh Assembly to boost the supply and demand of affordable broadband across the region.
While direct mail will be used as the primary means of communication, activity will include online advertising. There is also an option to extend the campaign for a further 12 months.
The process is being overseen by Broadband Wales' director of marketing, Andrew Peretz.
The Broadband Wales programme was launched by the Welsh Assembly in July 2002. It aims to create a broadband infrastructure across Wales by March 2007.
The Welsh government is eager to transform Wales into a more modern, information-led economy.
Broadband Wales is currently running an advertising campaign created by Welsh agency Blah d Blah. About 80% of Wales' population has potential access to broadband, but take-up is low.
Wales is not the first area in the UK to use marketing to increase broadband use. Earlier this year the Scottish Executive exceeded its target of establishing coverage across 70% of the country.
Key to meeting this target was an integrated campaign created by Edinburgh agency The Union.