In the present manuscript, the impact of doping of CdS QDs (~3.75 nm) on the optical and dielectric properties of a negative dielectric nematic liquid crystal (NLC), namely MBBA (4′-methoxybenzylidene-4-n-butylaniline) is probed through polarising optical microscope and frequency dependent dielectric spectroscopy. The planar and homeotropically anchored ITO sample cells are used for optical and dielectric studies. CdS QDs-MBBA composites are prepared by doping of 0.1 wt% and 0.3 wt% CdS QDs in MBBA, NLC. Optical textural studies have confirmed the significant improvement in homeotropic alignment but not the planar alignment of CdS QDs-MBBA composites as compared to pure MBBA sample. Both perpendicular and parallel components of real dielectric permittivity of MBBA are found to vary significantly as a function of dopant concentration albeit the dielectric anisotropy (∆ε) remained negative. In 0.1 wt% composite, the magnitude of ∆ε is increased by ~ 66% as compared to pure MBBA sample. But it returns almost to the same value of pure sample in 0.3 wt% composite. The spectral peak of short axis molecular relaxation in homeotropically aligned MBBA is found to shift (~4 to 5.5%) towards higher frequency side as a function of dopant concentration. The modulated optical and dielectric features of MBBA by CdS QDs could be due to the probable interaction between CdS QDs and MBBA molecules. We do believe that these nanocomposites would be useful in the tunable optoelectronic devices.