McNulty is planning a move to Singapore in the new year, and will leave Excel London on 20 December after five years at the venue.
The Excel London senior account manager will also be standing down from her position as board member at Eventia following a board meeting on 18 December. .
McNulty said: "The time has come to embrace an exciting new opportunity and I am thrilled at the prospect of a challenge overseas.
"I have loved working at Excel and I will be sad to leave, especially having worked with such a talented and committed team of amazing people. We have met and exceeded our targets and I can't imagine a better team to work with."
McNulty, who joined Excel London in January 2009 after a five-year stint at Novotel London West, plans to explore opportunities in Singapore's thriving business tourism market following her move in 2014.
The move will spark changes at Excel London including senior account manager Jamie Ades, who joined in May 2013, shifting from the corporate to the association market at the beginning of December.
Excel London will also recruit a new corporate business development manager.
The venue's executive director James Rees said: "Kirstie will be sorely missed in the team. She is an absolute rock – hard working and clients love her because she always goes the extra mile. We all wish her the best and we know she will be a success. It is clichéd but if she ever wants to come back, Kirstie will find an open door at Excel."
McNulty has been part of the team at a time when the venue has expanded to include the ICC London, which opened in 2010, and the confirmation of the 2015 European Society of Cardiology event, Europe's largest medical congress.
Meanwhile, McNulty's exit from the Eventia board coincides with a series of changes that mark the relaunch of the trade body after its merger with IVCA when an interim board takes over in January, before a members' re-election process in July.
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