A bicycle bottom bracket assembly comprises a first adapter, a first bearing, a second adapter and a second bearing. The first adapter extends along a first center axis of the first adapter. The first bearing comprises first rolling elements and a first outer race. The first outer race is configured to be fitted in the first adapter. The first outer race is slidable relative to the first adapter in both axial directions along the first center axis in a state where the first outer race is fitted in the first adapter. The second adapter extends along a second center axis of the second adapter. The second bearing comprises second rolling elements and a second outer race. The second outer race is configured to be provided in the second adapter such that the second outer race is a separate member from the first outer race.