It is currently a work-in-progress and not a complete game.
While there is no official release for the PSP, the dedicated homebrew community has developed several fan-made versions and technical workarounds to bring the Underground to Sony’s classic handheld. Undertale Psp Iso Download REPACK
: Includes the core story, turn-based combat system, and the "Mercy" vs. "Fight" mechanics. Portability It is currently a work-in-progress and not a complete game
: Includes the iconic music by Toby Fox, though some tracks may be compressed to fit the PSP's memory. Portability turn-based combat system