G-protein-coupled receptors (GPCRs) are key cellular components that mediate extracellular signals into intracellular responses. Genome mining revealed that Phytophthora spp. have over sixty GPCR genes among which a prominent class of twelve encoding novel proteins with a N-terminal GPCR domain fused to a C-terminal phosphatidylinositol phosphate kinase (PIPK) domain. This study focuses on two GPCR-PIPKs (GKs) in Phytophthora sojae. PsGK4 and PsGK5 are differentially expressed during the life cycle with the highest expression in cysts and during cyst germination, and at late infection stages. In P. sojae transformants that constitutively express RFP tagged PsGK4 and PsGK5, the fusion proteins in hyphae reside in small, rapidly moving vesicular-like structures. Functional analysis using gene-silencing showed that PsGK4-silenced transformants displayed higher levels of encystment and a reduced cyst germination rate when compared to the recipient strain. Moreover, GK4 deficiency (or reduction) resulted in severe defects in zoospore chemotaxis towards isoflavones and soybean roots. In contrast, PsGK5-silenced transformants exhibited no obvious defects in asexual development but oospore production was severely impaired. Both, PsGK4 and PsGK5-silenced transformants showed reduced pathogenicity. These results point to involvement of GKs in zoospore behavior, chemotaxis and oospore development, and suggest that PsGK4 and PsGK5 each head independent signaling pathways.