GreenSpace chief executive Paul Bramhill said Preston has been appointed as a GreenSpace trustee and, taking "an ambassadorial role to create a higher profile for parks".
Bramhill said Stockport parks manager Norman Hudson has also become a trustee and GreenSpace is looking to increase the number of trustees. Preston will also work as CABE Space enabler.
Parks consultant Sid Sullivan said: "I'm amazed Leeds let someone of Denise's quality go. She's such a great talker and negotiator."
In October, Preston received three Horticulture Week Landscape & Amenity Awards on behalf of the Leeds Parks & Countryside Service.