Abstract We present di‐ tert ‐butyl peroxide (DTBP)‐catalyzed long‐wavelength light‐induced Group 13, 14, and 15 elementalizations of alkenes and alkynes, through in situ production of tert ‐butyl radicals, followed by a hydrogen‐atom‐transfer process generating silyl, germyl, stannyl, alkyl, boryl, and phosphoryl radicals. This mild and photosensitizer‐free methodology employing blue (450 nm)/green (530 nm)/orange (600 nm) LEDs affords high chemoselectivity and broad functional group tolerance compared to conventional use of shorter‐wavelength light. Synthetic, spectroscopic, and computational data are consistent with a vibration‐mediated photolysis mechanism of DTBP involving electronic excitation from vibrationally excited ground states (S 0 μ n ) to the excited state (S 0 μ n →S n transitions), driven by ultraweak absorption of long‐wavelength visible light.