Disconcerting means unsettling — it throws you off balance, often because something is odd rather than bad. Concerning means causing worry about an outcome. A stranger knowing your name is disconcerting; a lump is concerning. The first disturbs your composure, the second your peace of mind.
The core difference
Both describe an uncomfortable reaction, but to different things.
- disconcerting — unsettling, disorienting: a disconcerting silence.
- concerning — worrying, suggesting a problem: a concerning trend.
The other concerning
Concerning also works as a preposition meaning "about" — a letter concerning your account. That older use is entirely standard, and some readers object to the adjective sense as a recent Americanism. It is common enough now to be unremarkable, but it is worth knowing the objection exists.
Choosing
If something is strange or unbalancing, use disconcerting. If it points at a real problem, use worrying or concerning — and worrying sidesteps the objection entirely.
