Petrie began her journalism career in radio, as a writer for Independent Radio News bulletins. She later joined TV3, where she worked variously as a reporter, news anchor and weather presenter on 3 News, as well as being a regular fill-in host on late night news programme Nightline.
Petrie moved to Canada in 2001, becoming a newsreader for the CTV News Channel and a substitute newsreader on the CTV morning programme Canada AM. During her time in Canada, she reported on the September 11 attacks for 3 News.
In late 2003, Petrie returned to New Zealand and joined TVNZ, initially as a fill-in presenter across all One News bulletins. She was on air when the Boxing Day tsunami took place, as well as during the 2005 London bombings; for this, as well as her earlier reports on the September 11 attacks, she was jokingly dubbed a 'disaster magnet' by former boss Bill Ralston.
- "Petrie, Dallow are One for news". New Zealand Herald. 10 December 2005. Retrieved 3 January 2019.
- "Wendy Petrie". NZ On Screen.
- "Newsreader back on board". New Zealand Herald. 20 April 2001. Retrieved 3 January 2019.
- "In the women's mags: Brad should talk to Wendy if he thinks he's got problems". New Zealand Herald. 3 September 2006. Retrieved 3 January 2019.
- September 11, 2001; New Zealand's TV3 6 O'clock news (Video). TV3. 11 September 2001.
- "Wendy Petrie's personal cancer crusade". New Zealand Woman's Weekly. 31 May 2016. Retrieved 3 January 2019.
- "New son for Wendy Petrie". The New Zealand Herald. Newstalk ZB. 31 January 2010. Retrieved 2 December 2011.