Transition-metal tetravalent manganese ions (Mn4+) as luminescence center of red phosphors have drawn much attention owing to their broad-band absorption extended from UV to blue regions and narrow red-emissive band. In the present work, a series of Mn4+-doped BaGeF6 red phosphors were obtained via hydrothermal method. X-ray powder diffraction, energy-dispersive X-ray spectrometer, scanning electron microscope, and photoluminescence spectra were employed to determine the crystal structure, composition, morphology, and photoluminescence properties of all samples. The prepared BaGeF6:Mn4+ samples demonstrate two dominant broadband absorption at near-UV (-366 nm) and blue regions (-470 nm) and intense red emissions (-635 nm) under 470 nm excitation. In addition, the morphology and the emission intensities were successfully controlled by adjusting doping concentrations, reaction times, reaction temperatures, barium sources, and surfactants. Concentration quenching and thermal quenching mechanisms were studied in detail. When the BaGeF6:Mn4+ red phosphor was introduced into the light-emitting diode, warm white light-emitting diodes (w-LEDs) were successfully fabricated, which have high color rendering index (Ra = 86.3) and low correlated color temperature (4766 K), indicating that the BaGeF6:Mn4+ red phosphor provides a good opportunity for application in w-LEDs.