Marie-Christine Lombard, chief executive officer of TNT Express, is leaving before the takeover by UPS is completed.
The company has appointed Bernard Bot as interim CEO.
The UPS takeover is now expected to be be completed in the Spring of 2013.
Lombard is leaving “to pursue an external career opportunity”, the company said.
Antony Burgmans, chairman of the supervisory board, said: “It is regrettable that Marie-Christine has decided to leave TNT Express now. We thank Marie-Christine for her contributions and wish her well for the future. This development has no bearing on the intended merger with UPS, which we expect to complete in early 2013.
“Moreover, the underlying business remains robust and continues to be well managed by an experienced Management Board. We have complete confidence in Bernard’s ability to lead the business and to see through the merger with UPS.”