In this study, we determined the suitability of lentogenic LaSota and naturally occurring avirulent I₂ vaccine strains of Newcastle disease (ND) virus for efficacious in-ovo vaccination of broiler chickens. A total of 114 embyonated eggs divided into five groups (A, B, C, D and E) consisting of 25 eggs in each of groups A and B, 20 eggs in each of groups C and D and 24 eggs in group E were used in the study. Eighteen-day-old embryonated eggs in group A were vaccinated in-ovo with ND-I₂ vaccine while the same age of embryos in group B were vaccinated with ND-LaSota. Thirteen-day-old embryonated eggs in groups C and D were vaccinated with ND-I₂ and ND-LaSota respectively. Group E served as unvaccinated control. There was significant difference (p < 0.05) in percentage hatchability between the vaccinated and control groups. Highest hatchability (64%) was recorded in group A when compared to other vaccinated groups (B [36%], C [10%] and D [5%]). The difference in embryonic mortality between groups was also statistically significant. The lowest mortality rate (36%) was recorded in group A when compared with group D (95%), group C (90%) and group B (64%). In spite of the pre-existing maternal antibody, the in-ovo vaccinated embryos seroconverted to protective antibody titres (GMT of 5.7 ± 0.00 - 7.30 ± 2.08) when compared with the control group E which had non protective antibody titre GMT of 3.00 ± 2.75 and decayed faster in chicks after hatching. There was significant rise in antibody titre (anamnestic response) in all experimental chicks following booster vaccination on day 37 post hatching. It is concluded that the ND vaccines (LaSota and I₂) used for the in-ovo vaccination were pathogenic for chick embryos, however, ND-I₂ vaccine was better tolerated when administered to 18-day-old chick embryo.