An efficient route for the synthesis of novel spiro[indole-pyrimidine]ones in high to excellent yields has been investigated through one-pot reactions of phenacylidenetriphenylphosphoranes, oxindoles, and thiourea. Their antibacterial activities were studied against Gram-positive bacteria and Gram-negative bacteria using disc diffusion method. The results showed that most of the synthesized compounds are effective against Gram-positive bacteria.