A bicycle bottom bracket assembly having a rotational central axis includes a support member, a bearing unit and a radially inward force reducing structure. The support member includes a hanger mounting portion and a bearing mounting portion. The bearing mounting portion is configured to be at least partly positioned within a hanger part of a bicycle frame. The bearing unit includes an outer race, an inner race and at least one roller element disposed between the outer and inner races in a radial direction with respect to the rotational central axis. The outer race is fixed to the bearing mounting portion of the support member. The radially inward force reducing structure reduces a radially inward force being transmitted to the bearing unit.