While at McCann, she helped conceive Tag Ideation, a lifestyle marketing practice group, developing a set of proprietary research tools and co-designing a proprietary branding model. She returned to Nigeria in 2004.
Since returning to Nigeria, Nnenna has worked in advertising, event planning and content development for international brands like Standard Chartered, MTV, Coca-Cola, BAT, Celtel, Motorola and Microsoft, as well as local brands such as Paga, FCMB, V Mobile, Virgin Nigeria, Cross River State Tourism, Oando and First Bank.
After positions at Chris Parkes Marketing Solutions, Small World Media and TBWA/Concept, Nnenna joined ZK Advertising in 2007. In her time at ZK, she developed comprehensive strategies for clients including Zain, Dangote and several PZ Cussons brands. In her second year at ZK, Nnenna also took on the role of Creative Director, developing award-winning advertising for a variety of clients.
In 2011, Nnenna and her partners took over the agency, rebranding it to Yellow Brick Road. She is also a founding partner in Blackbox, a strategic marketing consultancy.