The former Prime Time reporter welcomed viewers with a standing piece to camera in the RTE newsroom before taking up residence behind a desk.
She made her 9am debut in a simple white blouse with a black jumper.
Shanley has said that the programme isn't a copy of TV3 rival Ireland AM.
"Morning Edition is a very different product because it comes from RTE News with all the resources of that department: weather, business and sport," said Keelin.
"I watch TV to learn about things, and there will be a lot of news and information each day," she said.
RTE hopes that the show will draw audiences in offices around the country by offering an alternative to the rolling Sky and BBC news shows that tend to act as a backdrop for many companies.
The newly-designed set is formal and based on royal and sky blue hues with a standing podium for sports presenters.
"I suppose a likely audience are those people at home and the unemployed who would previously have been working. We're only interested in getting the show on air at the moment, and getting it working. Audience is something we will see about in time," said the Trinity graduate.
Meanwhile, Pat Kenny claimed he has no fear of losing listeners to the new show.
"I wish presenter Keelin Shanley and the show the very best of luck. My programme has nothing to fear from the show's success," he told the Herald.
"Our shows are two different products."
-- ALAN O'KEEFFEE