We report an available route for the synthesis of poly(methacrylic acid) (PMAA) macromonomers/N-acetyl-L-cysteine (NAC)-co-capped CdTe quantum dots (QDs) toward multicolor fluorescent patterns and warm white LED devices. The properties of the as-prepared CdTe QDs herein were thoroughly investigated by Fourier transform infrared spectra (FT-IR), ultraviolet-visible (UV-vis), photoluminescence (PL), X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. We have found that the PMAA/NAC-capped CdTe QDs exhibited stable and strong photoluminescence (PL) with a narrow size distribution and a high quantum yield (QY) of ∼45%. Moreover, the as-prepared CdTe QDs demonstrated a quick growth rate and favorable fluorescent stability without any aggregation and phase separation when they were blended with a polymer matrix. Subsequently, by virtue of their excellent polymer-compatibility, we extended the water-soluble PMAA/NAC-capped CdTe QDs as “fluorescent ink” for multicolor fluorescent patterns by silk screen printing, which may find application in the anti-counterfeit field. In addition, we explored the robust CdTe QDs as “red phosphor” to fabricate a white LED device, the resulted LED emitted a higher rendering color index (CRI) warm white light compared to the conventional phosphor-only LEDs. It is believed that the route reported here could offer an available pathway to achieve robust QDs for diverse applications.