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Broadband near‐infrared (NIR) luminescent materials have received notable attention due to their distinct photophysical properties for designing NIR light‐emitting diodes (NIR LEDs). Here, a series of Ca3−xLuxGa2+xGe3−xO12:Cr3+ (CLGGG:Cr3+) (x = 0–1) NIR‐emitting garnet phosphors with an emission range of 660–1200 nm are successfully developed and their lattice parameters are structurally analyzed. Upon 460 nm blue light excitation, the NIR phosphors exhibit both a substantial spectral broadening (FWHM: 129→267 nm) and a redshift of 37 nm (766→803 nm) with cosubstitution of [Lu3+–Ga3+] pairs for [Ca2+–Ge4+] sites. Furthermore, their luminescence thermal stability is substantially improved, maintaining ≈90% of the original photoluminescence intensity at 150 °C, owing to shrinkage of the second coordination sphere and rigid lattice, which are strongly associated with Cr3+ trade‐off occupancy and local structure evolutions. The relation between the trade‐off site occupation of Cr3+ in GaO6/CaO8 polyhedrons and the NIR emission is also clarified by evaluating the decay and electron paramagnetic resonance behavior of Cr3+ at different sites. The broadband NIR phosphors investigated here can serve as auspicious luminescent converters for phosphor‐converted NIR LEDs and can provide an inspiring platform for future studies. [ABSTRACT FROM AUTHOR]