The US President said he had brought in Bill Stepien, a field director for his 2016 campaign, in place of Brad Parscale.
Mr Parscale’s future had been in serious doubt for weeks as Mr Trump was reportedly left furious when his return to the campaign trail flopped at the end of June.
A planned rally in Tulsa, Oklahoma, fell well short of expectations after Mr Parscale predicted huge crowds.
Mr Parscale will stay on as senior adviser after being replaced as campaign manager.
Announcing the decision, Mr Trump said: “Brad Parscale, who has been with me for a very long time and has led our tremendous digital and data strategies, will remain in that role, while being a Senior Advisor to the campaign.”
Mr Parscale had boasted that more than one million people registered to attend the Tulsa rally, but fewer than 6,200 showed up at the arena according to the local fire department.
After the rally, Mr Parscale went on Twitter to blame a blocked security gate, protesters and the media for the disappointing turnout.