However, I don't own a Nikon D3300, but a D5100, D300 and a D600 and the autofocus works fine on all three. I did some more googling about this and found out that there are two types of Sigma 105mm: an old one that needs a focus motor in the camera (the D3300 doesn't have one) and a newer one (actually the current one) that has an ultrasonic motor in the lens. The latter should definitely work with the D3300 (I have the lens with the US motor).