An adjustable kettlebell includes a threaded shaft having a narrowed neck segment formed on one end portion and having a base plate attached to the other end portion, two or more weight members each having a slot for receiving the narrowed neck segment of the shaft, and each having an enlarged opening communicating with the slot for receiving the shaft and for retaining the weight members to the shaft when the weight members are offset from the narrowed neck segment of the shaft, and a lock nut is engaged with the shaft for quickly retaining the weight members to the shaft after the weight members have been disengaged from the narrowed neck segment of the shaft.