This protocol provides a liquid production method for the propagation of bacteriophages (phages), wherein bacteria and phages are co-incubated in liquid medium under constant agitation. The advantages of this protocol are its easy use and the low costs, as there is no specialized equipment required. Besides the fact that not all phages can be propagated using a liquid approach, another disadvantage of this protocol is the strong dependence on the bacterial growth rate which will result in different protocol durations (e.g., 25:15 h for P. aeruginosa).