Germ granules, also known as P granules in Caenorhabditis elegans,are phase-separated cellular bodies that are frequently found at the perinuclear region of germ cell nuclei in various animals. However...P granules are phase-separated liquid droplets that play important roles in the maintenance of germ cell fate in Caenorhabditis elegans. Both the localization and formation of P granules are highly dynamic, but mechanisms that regulate such processes remain poorly understood. Here, we show evidence that the VASA-like germline RNA helicase GLH-1couples distinct steps of its ATPase hydrolysis cycle to control the formation and disassembly of P granules. In addition, we found that the phenylalanine-glycine-glycine repeats in GLH-1promote its localization at the perinucleus. Proteomic analyses of the GLH-1complex with a GLH-1mutation that interferes with P granule disassembly revealed transient interactions of GLH-1with several Argonautes and RNA-binding proteins. Finally, we found that defects in recruiting the P granule component PRG-1to perinuclear foci in the adult germline correlate with the fertility defects observed in various GLH-1mutants. Together, our results highlight the versatile roles of an RNA helicase in controlling the formation of liquid droplets in space and time.