Middleton was appointed to the role in 2020 after a stint as the organisation’s strategic lead - international and capability, and strategic lead for education and youth.
She took over from Mark Ward who left in May 2020, after 16 months in the job.
W&P board chair Pahia Turia said although it was sad she was moving on, the board would continue to hold her in high esteem and respect her decision.
“We know it was a difficult choice for Hannah and that she will have given the decision full consideration,” Turia said.
“Ultimately, what is best for our children and loved ones should always be the path taken and I trust this is the case for Hannah right now,” he said.
He thanked Middleton for all she had done for the Economic Development Agency and the positive impact she had made in the role.
“I cannot overstate how much we have appreciated Hannah’s efforts, enthusiasm and capability.”
W&P is now undertaking a recruitment process.
Acting chief executive Jonathan Sykes will remain in the position until the new chief executive appointment is made.