Can a youth criminal record still make me inadmissible to Canada as an adult?

It depends on how the youth matter was handled, because Canadian and comparable foreign youth justice systems treat young offenders differently from adults in ways that can carry over into an immigration assessment. A finding of guilt handled entirely within a youth justice framework, with its own protections and record-keeping rules, is not automatically treated the same as an adult conviction, and in many cases will not create inadmissibility at all once those youth protections apply.

That said, the details matter a great deal. If a young person was tried and sentenced as an adult, or if the foreign system involved doesn't distinguish youth matters the way Canada's does, an immigration officer may still find an equivalent adult-level consequence. Records that are meant to be sealed, expunged, or otherwise protected under youth justice rules also need to actually have that status confirmed — an old record that technically should no longer be accessible can still surface and cause problems if it wasn't properly dealt with at the time.

Anyone with a youth record from Canada or elsewhere should get the specific disposition reviewed against current immigration rules before assuming it either does or doesn't matter, since the outcome depends heavily on exactly how that matter was resolved.