The non-enzymatic electrochemical detection of glucose and aqueous ammonia was carried out using ternary bio-nanocomposites. A co-precipitation method was employed to synthesize cadmium stannate nanoparticles, while bio-nanocomposites of polyaniline–cadmium stannate–chitosan were synthesized via the chemical oxidative polymerization technique. Functional group analysis, structural and morphological studies were further carried out via Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and scanning and transmission electron microscopy techniques. The electrode kinetics and electrochemical properties were validated via cyclic voltammetry, electrochemical impedance spectroscopy (EIS), and chronoamperometric techniques. The sensing properties of the electrocatalysts were explored using cyclic voltammetry and amperometry for the detection of glucose and ammonia solution of varying concentrations using NaOH electrolyte. The electrochemical activity of the electrocatalysts were optimized using different weight percentages of chitosan, and bio-nanocomposites of polyaniline/cadmium stannate/chitosan (10%) showed excellent electrocatalytic and electrochemical activities. Moreover, the bio-nanocomposites have a low detection limit and short response time toward different concentrations of glucose and ammonia solution. Apart from these studies, the sensors have also been evaluated for an anti-interference study. The developed novel sensors present significant potential to be efficiently utilized on a large scale, as they also show effective stability and reproducibility, along with a high level of sensitivity for the given target analytes.