If you always watch with subtitles, it won't be very effective, because your attention will be focused on the subtitles instead of Japanese. You'll learn only a few words after a long time (this happened to me). However, I've heard that if you watch once with subtitles, then the same episode raw and repeat it multiple times, you'll learn more and eventually understand the whole content in Japanese. Obviously that takes a lot of patience and effort, I tried once but ended up getting tired of the same episode and gave up in the beginning,