The best replacement for mientras is mientras que.

The best alternatives to mientras are rated as following:
★★★★★  mientras que
★★  cuando
★  durante

Your alternative for mientras is not listed? Suggest!
Speaking about mientras, one probably shouldn't forget about imperfect.

Other search terms related to mientras and their ratings are:
★★★★★ imperfect
You have in mind a companion for mientras and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of mientras in all years. Click on graph for more.
mientras
mientras que
cuando