Langmead joined the NatMag-owned Esquire in March 2007 as the title looked to gain ground on its rival GQ.
Langmead helped to drive up Esquire's circulation from 53,537 when he joined to 58,151 copies between January and June this year. However, it still lags significantly behind GQ, which has a circulation of more than 120,000.
NatMag said Dan Davies, Esquire's deputy editor, will move into an acting editor's role from 8 October until a replacement for Langmead is announced.
During Langmead's tenure, the title introduced guest editors to the title as well as founding the yearly Esquire Man At The Top Awards and the Best Dressed Real Man competition.
Notable covers during Langmead's time as editor include a cover of Barack Obama with the strapline "Can this man save the world?" and a nude cover of Katy Perry with a cartoon of fiancé Russell Brand propping up the barcode.
Langmead will take on the role of editor-in-chief for Mr Porter, Net-A-Porter group's menswear site.
Langmead, speaking of his time at Esquire, said: "I've loved working at Esquire for the past three years and have felt extremely proud to be at the helm of such an exciting, creative and innovative brand.
"I am sad to go but I leave Esquire knowing that it is in the capable hands of a passionate, brilliant and hard-working team. I am confident that it has a great future and will grow from strength to strength."
Meribeth Parker, Group publishing director, said: "Jeremy is a talented Editor who has given a new lease of life to Esquire and helped transform this iconic UK brand into an authoritative voice on men’s style and fashion.
"He will be hugely missed by those who have worked with him at NatMag and we wish him well in his new role."
In April Net-A-Porter founder Natalie Massenet sold her share of the business for £50m to Swiss luxury goods group Richemont.