As soon as you can and they are interested! I started my daughter at 3 and she really took to it quickly. It's important to keep it fun though. We go to the basement or behind the house to shoot, sometimes she will shoot five or six arrows and say I'm all done daddy, and that's okay! Other times she will want to keep shooting as long as she can. I've found that shooting at fun targets really helps keep her interested, her favorite targets are balloons. I usually use 12" so she has lots of hits. On the other hand, my son is four and hasn't really shown much interest yet, I'm not going to push him on it, I think he will find his way to shooting in his own time (at least I hope he will!)