MJZ, which is headed by the executive producer Debbie Turner, has offices in London, New York and Los Angeles.
Gilchrist left Thomas Thomas last Friday and signed a contract with MJZ early this week.
Gilchrist, who joined Thomas Thomas in 2005, started his career at VTR and later moved to Fallon. After five years, he left to study at the International Film School in Rockport, Maine, becoming a director in September 2004.
Since then, he has shot ads including Harvey Nichols' "backstage", Tango's "bravo" and Waitrose's "picnic".
Recent awards include a silver at Cannes for "bravo", a silver at Eurobest for "backstage", and BTAA and Creative Circle nominations for Comfort's "nudist".
Gilchrist said: "MJZ is a brilliant production company. It's the kind of place that will allow me to do my best work and take me to the next level."