I feeling like there is really no such thing as 100% waterproof when it comes to mascara or eyeliner, but this one comes pretty close. I've been caught in a heavy downpour wearing this and it remained intact. Now one thing I will say is the handle is not my favorite, I am a bigger fan of liquid pens. I would occasionally dip an eye liner brush into the bottle so I have a longer brush stem to work with. The one that it comes with is short and fat and just doesn't sit well in the hand. Overall the actual formula is worth it for the price.