Later, at Citytv Toronto, she worked as a writer, reporter and co-anchor, with Gord Martineau, of evening newscast CityPulse at 6. There she hosted an afternoon programme, Sweet City Woman.

In 1980, a documentary camera followed her pregnancy and the birth of her son Nicholas.

At Citytv's daily talk show CityLine, Petty established herself as one of Canada's foremost television talk show hosts. She left her news anchor position to concentrate on CityLine.

In 1989, Petty moved to CFTO and the Baton Broadcasting System. Her hour-long general interest talk show, The Dini Petty Show, aired until 1996. It was during this period that Petty offended the Jewish community by her use of the word "Hymie" to describe a cheapskate husband of a guest. She later apologized for any offence she caused.

In the 2000s, Petty hosted Weekends with Dini Petty, a syndicated weekly radio program focused on health and wellness for baby boomers. Sheila Copps succeeded her as host of Weekends.

Petty wrote a children's book, The Queen, the Bear, and the Bumblebee.