An angle adjustable bicycle saddle contains a seat post, a cushion, and a locking unit. The seat post includes an inwardly curved groove having multiple protrusions, and the seat post includes multiple troughs. The cushion includes a body and a cap. The body has a curved holder, an arcuate abutting projection, multiple engagement portions, and multiple through holes corresponding to the multiple troughs. The cap is covered on the curved holder of the body so that the curved holder has a hollow portion. The locking unit includes multiple fixing elements and multiple stepped nuts. A respective fixing element is inserted through a respective trough and a respective through hole. A first end of a respective fixing element is adjustably received in a respective trough, and a second end of the respective fixing element is accommodated in the hollow portion of the curved holder.