Helopeltis theivora, a severe pest, damages young tea plant buds, reducing black tea quality. We studied Tocklai vegetative clones TV1 and TV23 at four infestation levels (none, low, moderate, high). Results showed significant differences in various biochemical qualities. Moisture dropped from 3.04% to 2.13%, dry matter increased from 96.96% to 97.86%, caffeine decreased from 3.71% to 2.50%, DPPH antioxidant activity declined from 70.44% to 51.26%, TSS decreased from 44.60% to 36.78%, and total polyphenol content decreased from 22.38% to 14.99%. TV1 had the highest TF:TR ratio (1:10.89) in non-infested samples, while TV23 had the lowest (1:7.63) in heavily infested samples. Brightness (%) ranged from 33.07% to 46.07%, and color index from 4.2% to 5.32%. Organoleptic qualities (brightness, briskness, strength, quality) decreased with increasing infestation, highlighting the negative impact of Helopeltis theivora on tea quality.