Police said the crash happened in the Mount Greenwood Heights neighborhood's 3800 block of West 115th Street just after 10 a.m.
A 32-year-old man was driving a motorcycle westbound on 115th Street when he struck the back of a bus in the same lane, police said. He was transported to Christ Hospital in serious condition for a leg injury.
No other injuries were reported and no citations were given. CPD's Major Accidents Unit is investigating.
Police did not immediately provide further information about the crash.