A Newcastle disease surveillance program was conducted at live bird markets in Korea to expand our epidemiologic understanding of the disease in Korea. During the surveillance program, 10 lentogenic Newcastle disease viruses (NDVs) were isolated and identified from apparently healthy chickens and ducks at live bird markets. The lentogenic viruses had sequence motifs of either ¹¹²GKQGRL¹¹⁷ (n  =  8) or ¹¹²GRQGRL¹¹⁷ (n  =  2) at the F0 cleavage site. Sequencing and phylogenetic analyses of NDV isolates based on the hypervariable region of the F protein revealed two different genotypes: genotypes I (n  =  8) and II (n  =  2). Genotype I viruses were most closely related to the NDV V4 strain (n  =  7) or the NDV Ulster 2C strain (n  =  1). In contrast, genotype II viruses clustered with the NDV vaccine strains (LaSota and VG/GA) that are commonly used as live vaccines in Korea. The epidemiologic importance of NDV at live bird markets in Korea is discussed.