Fletcher retired as an MP in 1999, having been elected Mayor of Auckland City at the 1998 local-body elections. She was the second woman to hold the office, after Cath Tizard. Fletcher's mayoralty was characterised by the decision to progress with the Britomart Transport Centre in downtown Auckland. In 2001 she was defeated by John Banks, another former National MP. She continued her opposition to Banks in the following years, particularly opposing the Eastern Transport Corridor, which Banks had proposed as a major motorway, and which she noted she had been opposing for more than a decade by then.