A keyed cylinder assembly (10) includes a keyed cylinder (3) mounted in a door lock (1) and including a hollow body (31) and a cylinder plug (32) rotatably received in the hollow body (31). The cylinder plug (32) includes an annular groove (327) formed in an outer periphery (320) thereof. The keyed cylinder (3) further includes an arresting member (37) received in the hollow body (31) and having an inner end (371) received in the annular groove (327). The keyed cylinder assembly further includes a first key (4) insertable into a keyway (323) of the cylinder plug (32) to operate both a latch bolt (12) and a deadbolt (13) of the door lock (1). The keyed cylinder assembly (10) further includes a second key (5) insertable into the keyway (323) of the cylinder plug (32) to operate the latch bolt (12) only.