Objectives <p>Fusion (F) protein is crucial for facilitating viral entry into host cells and contributes to the virulence of Morbilliviruses. Serial passaging of the <i>Peste Des Petits Ruminants</i> virus (PPRV) in nonnative hosts can lead to mutations that potentially reduce pathogenicity. Hence, this study aimed to investigate the effects of serial passaging of a Bangladeshi strain of PPR virus in Vero cells on the Fusion protein and pathogenicity</p> Materials and methods <p>PPR viruses were initially isolated from natural PPR outbreaks, confirmed through reverse transcriptase polymerase chain reaction (RT‒PCR), passaged to the 9th passage in Vero cells, sequenced, and preserved in a previous study. The 9th passage virus from the repository was utilized as the viral inoculant for further passaging in Vero cells, and the 60th passage was completed. The presence of PPR viral RNA was confirmed in tissue culture fluid (TCF) by RT‒PCR at different passage numbers. TCF at the 60th passage was sequenced and used for immunogenicity studies via live animal experiments, and subsequent immunity was measured via cELISA.</p> Results <p>Comparative analysis of the sequences from the 9th and 60th passages, along with other sequences, revealed substitutions of 14 nucleotides (nts) and 4 amino acids (aa) within the leucine zipper structure of the fusion protein. Notably, live animal experiments demonstrated the occurrence of protective immunity.</p> Conclusion <p>This study suggests that amino acid substitution and genetic divergence may positively affect viral virulence, highlighting their importance in the development of a potent vaccine.</p>