On POSIX there is that risk, yes. As for Windows, the termination is based on the process handle instead of the PID, but I am not sure if that makes a difference. The risk of reusing the PID/handle is not related to this issue though. The solution I propose just ignores ERROR_INVALID_HANDLE and makes it an alias for "process is already gone". It does not involve preventing the termination of other process handles/PIDs (FWIW in order to do that in psutil I use PID + process' creation time to identify a process uniquely).