Silkworm Bombyx mori L. (Lepidoptera: Bombycidae) is a monophagous insect that feeds only on mulberry leaf. During rearing, shortage of a variety may engender a shift to another available mulberry variety to complete the rearing process. This study was carried out to assess the effect of host shift on B. mori fifth larval instar and the quality of cocoon produced. Silkworm eggs incubation and rearing of larvae were carried out following the standard procedures. There were four treatments consisting of different feeding components: sole mulberry variety S30, sole mulberry variety S14, host shift from mulberry variety S30 to S14 and host shift from mulberry variety S14 to S30. The treatments were arranged in a Completely Randomized Design with three replicates. At the fifth larval stage the worms were mounted on mountage and the spurned cocoons were harvested five days after. Host shift from mulberry S30 to S14 gave the highest fifth larval weight (2.29 ± 0.0 g) which was significantly higher than 1.99 ± 0.02 recorded on S14 sole feeding. The smallest single cocoon weight (1.07 ± 0.01 g), single pupal weight (0.96 ± 0.02 g) and single shell weight (0.10 ± 0.01 g) were obtained from sole feeding on mulberry S14.There was no significant difference in the total cocoon weight across the treatments. Silkworm larval survival, larval developmental period and number of cocoon formed were not negatively influenced either by sole feeding or shift in varietal feeding. Therefore, rearing process of silkworm that commenced with S14 or S30 can be completed with either of the varieties in the absence of one.