Can I get Steam achievments with long war mod on XCOM?

Solution 1:

Yes, at least with some achievements.

Modding XCOM doesn't disable achievements. I know this from personal experience- I got an achievement (jumping really high with the jumpylegs gene mod) while playing Long War.

However, even though the achievements aren't specifically disabled, some may still be broken or impossible due to the changes in Long War. Along with the extra difficulty of Long War and the extra time needed, you may be better off using the vanilla game to get your achievements.

Solution 2:

I've got "Pain in the neck" after stunning an EXALT dude (never did it in vanilla) so the answer is yes.