An alternative anthelmintic diatomaceous earth (DE) was evaluated for its ability to inhibit the migration of Oesaphagostomum dentatum larvae using migration and inhibition assays in vitro in unsheathed and exsheathed third stage larvae. The experiments were tested in 24-well plates at room temperature with five replications per treatment using different DE concentrations of 0.1 mg/ml, 0.3 mg/ml and 1mg/ ml. About 120 larvae per well were deposited on a larval migration apparatus consisting of 20 μm nylon mesh filters and incubated in 2, 4, 16, 20 and 24 hr under different treatments and another 2 hr to allow the migration of active motile larvae. The percentage inhibition were statistically analyzed. The highest inhibition was 78.20%, observed when DE was given at a dose of 0.3 mg/ml after 24 hr (P˂0.001) for exsheathed larvae and 67.60% (P˂0.01) with unsheathed larvae under 1 mg/ml concentration of DE after 24 hr. DE was more effective in exsheathed larvae at 0.3 mg/ml after 20 hr with 61.60% inhibition (P˂0.01). With unsheathed larvae, DE had a significant effect at 1 mg/ml exposed within 24 hr with 67.60% inhibition (P˂0.01). The larval migration/inhibition assay presented in this study showed the inhibitory effects of DE on O. dentatum.