High-density　polyethylene　(HDPE)　pipes　have　become　the　preferred　water　pipes　in　nuclear　power　plants.　Since　the　butt　fusion–welded　joint　of　HDPE　pipes　is　a　weak　link　of　a　piping　system,　it　is　essential　to　study　the　creep　properties　of　the　welded　joint.　In　this　study,　the　creep　properties　of　the　welded　joint　of　HDPE　pipes　were　studied　using　a　nanoindentation　creep　test.　The　test　results　showed　that　the　weakest　creep　resistance　was　not　located　in　the　weld　center,　but　was　a　little　away　from　the　weld　center.　The　power-law　creep　constitutive　model　was　constructed　at　different　locations　of　the　welded　joint　based　on　the　test　results.　In　addition,　the　hardness　of　the　welded　joint　was　tested.　The　results　showed　that　the　hardness　of　the　welded　joint　could　reflect　the　creep　resistance　of　the　welded　joint.　©　2021,　International　Institute　of　Welding.