He is best known as the director of critically acclaimed shorts Between the Lines and Bait as well as most awarded Kenyan film in history, Supa Modo.
That same year, he made his directorial debut with the film Supa Modo, which was critically acclaimed.
[5] It was later selected as the Kenyan entry for the Best Foreign Language Film at the 91st Academy Awards, but it was not nominated.
[8] His television work includes commercial advertisements for Pascha milk and Santa Maria, Kenyan food brands.
Wainaina has directed nine Africa Magic Original Films (AMOF) and a TV sitcom titled Classmates.
The series stars Wakio Mzenge, Nyokabi Macharia, Ainea Ojiambo, Maqbul Mohammed, Martin Githinji, Peter Kawa, Benson Ojuwa, Nick Kwach, Emmanuel Mugo, Angela Mwandanda, and Sam Psenjen.