London Irish, who lie just above the Premiership relegation place, issued a statement confirming Edwards had left his role at the Madejski Stadium.
"We would like to thank him for his efforts over the last six months and wish him well for the future."
There had been speculation Edwards might quit his role as Wales defence coach as the former Ireland Rugby League international had not been appointed to the Lions staff for the tour of Australia by Warren Gatland.
The New Zealander is Edwards' boss in the Wales set-up but the latter's failure to make the Lions coaching team had led to speculation that their partnership might be coming to an end.
But after talks with Lewis, Edwards has given up his other work to concentrate full-time on Wales.