Ericulture is mainly confined to North-Eastern region of India. In the present investigation, eco races of eri silkworm viz., Borduar, Barpathar, Khanapara, Mendipathar, Titabar and locally available commercial C2 breed were reared on four castor genotypes such as GCH 4, GCH 7, DCH 519, TMV 5 in comparison with local castor variety to evaluate the biochemical attributes of different castor genotypes and its influence on economic parameters of eco races of eri silkworm when reared on different castor genotypes. The study was carried out during the year 2019-2022 at department of Sericulture, TNAU, Coimbatore to identify suitable race for Tamil Nadu condition and the experimental design used for the study is FCRD (Factorial Completely Randomized Design) with four replications. The study revealed that, the castor genotype GCH 4 revealed higher level of biochemical constituents’ viz., crude protein (29.07 %), soluble protein (27.17 mg/g), total carbohydrate (39.21 %), crude fat (1.12 %) and ash content (4.73 %) followed by DCH 519 and least was recorded in TMV 5. Influence of castor genotypes on rearing of eco races of eri worms stated that leaves of GCH 4 recorded significantly maximum economic parameters followed by DCH 519 and local castor variety. Among the eco-races, Borduar registered best economic parameters followed by C2 breed in which both were on par with each other compared to other eco-races. The interaction between castor genotype x eri silkworm eco races, Borduar eco race of eri silkworm reared on the leaves of GCH 4 genotype found best for all parameters followed by GCH 4 x C2 breed and the lowest was recorded in TMV 5 x Barpathar.