A tool assembly (10), for example a hydraulic or pneumatic hammer assembly, comprises a housing (11) defining a chamber (16), a reciprocating work tool (20) arranged in the chamber for cyclical movement in a work stroke and a return stroke, and a tool retention member (80) arranged to restrain the work tool at the end of the work stroke. The tool assembly (10) includes a shock absorber arranged to absorb impact from the work tool at the end of a stroke. The shock absorber comprises an annular resilient flange (102, 154), which may be cantilevered from the tool retention member (80) to absorb impact at the end of the work stroke or may be provided on a bushing (150) arranged to absorb impact at the end of the return stroke. The shock absorbing flange reduces the transmission of shocks into the tool assembly, thereby providing increased life for tool assembly components.