A unidirectional ratchet wrench has a head and a ratcheting assembly. The head has a stationary jaw and a ratchet jaw. The stationary jaw is formed on and protrudes from the head and has an undulating surface. The ratchet jaw is formed on and protrudes from the head and has an arced slot formed in an inner surface of the ratchet jaw. The ratcheting assembly has an engaging tab being movably mounted in the arced slot and selectively engaging and disengaging a tool head with the inner surface of the stationary jaw when the wrench is respectively rotated in drive and non-drive directions.