Chilli powder, a widely used spice in global cuisine, faces rampant adulteration, posing significant health risks to consumers. One common adulterant is ferric oxide red, challenging to identify through visual inspection alone. To address this, a study was conducted to detect ferric oxide red in chili powder using various analytical techniques. Samples of chili powder, sourced from diverse locations, were adulterated with varying amounts of ferric oxide red. Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and ultraviolet–visible spectroscopy (UV–Vis) were employed for analysis. FTIR spectra revealed characteristic peaks of chili powder at 1385 cm−1, 1600 cm−1, and 2935 cm−1, alongside peaks indicative of ferric oxide red at 460 cm−1 and 540 cm−1. Raman spectra displayed peaks at 260 cm−1, 615 cm−1, and 1315 cm−1 for chili powder and at 225 cm−1, 306 cm−1, and 670 cm−1 for ferric oxide red. UV–Vis spectra exhibited an absorption band at 478 nm for ferric oxide red. Elemental mapping analysis further differentiated adulterated and unadulterated samples. Principal component analysis (PCA) and soft independent modelling of class analogy (SIMCA) effectively distinguished between them based on spectral data. These findings underscore the efficacy of the proposed analytical methods in detecting ferric oxide red adulteration in chilli powder, ensuring its safety and quality.