I've worn a sporran with jeans...one of the leather Stillwater Nightstalker ones, specifically. Just needed the extra cargo capacity and the sporran was handy...why not? Several people recognized it as a sporran and commented that it was a good idea. Lots of people asked what it was and also commented that it was a good idea...and a more manly alternative to a fanny pack/butt bag (as usual, sorry UK residents, it's still called a fanny pack in these here parts).

Mind you, this was on casual occasions...not dressy or even semi-dressy...though I don't see the harm. The current crop of suits and sport coats that I see are cut rather short in the body so a certain visual balance could be had by wearing a sporran.

Best

AA