Mugambi landed his first acting gig at age 5, as the little drummer boy in his nursery school Nativity. The reviews were excellent. His career would really begin decades later, with appearances in plays and musicals in different stages in Nairobi. It's when he found himself jobless in America in the middle of the 2008 recession that things got exciting. He joined Philadelphia’s acting scene, appearing in independent stage plays and short films, and telling stories about American history to tourists in the summer.
On returning to Nairobi, he landed principal roles in M-Net’s pan-African TV drama 'Changes', and the celebrated Kenyan films 'Nairobi Half Life' and 'Stories Of Our Lives'. After gaining some writing experience on the 'Village Series' of comedy musicals, he created, co-wrote and co-directed 'Groove Theory', a musical drama TV series that ran for two seasons on regional cable TV.
In 2014, Mugambi curated and directed 'Stories From The Mall', a theatre tribute to the events of the 2013 Westgate terrorist attack. In 2015, he co-wrote 'Kati Kati' a feature film co-written and directed by Mbithi Masya. Kati Kati premiered at the Toronto International Film Festival 2016 where it was awarded the FIPRESCI Prize. It went on to win the award for Best Film at Sweden's CinemAfrica Festival, a New Voices/New Visions Special Mention at the Palm Springs International Film Festival and the award for Best East African Film at the Africa Magic Viewers' Choice Awards.
In 2017, he co-wrote 'Supa Modo', a family film directed by Likarion Wainaina, which premiered at the 68th Berlin International Film Festival 2018, and was awarded a Special Mention from the Generation Kplus Jury. Supa Modo continues a spirited worldwide festival run and is still winning the adoration of viewers and critics.