Independent developers like Sticks456546 have uploaded builds designed for the PSP. These are free fan-made creations and are not official "repacks" of the retail game.
Many versions only cover the "Ruins" section or specific boss battles rather than the full game. Input Latency: Undertale Psp Iso Download REPACK
was never officially released for the PlayStation Portable (PSP), unofficial ports and homebrew versions exist that allow players to run the game on the handheld via custom firmware. Key Features of Undertale for PSP (Homebrew/ISO) Undertale Psp Iso Download REPACK