Plant responses to drought stress have been analyzed extensively to reveal complex regulatory gene networks, including the detection of water deficit signals, as well as the physiological, cellular, and molecular responses. Plants recognize water deficit conditions at their roots and transmit this signal to their shoots to synthesize abscisic acid (ABA) in their leaves. ABA is a key phytohormone that regulates physiological and molecular responses to drought stress, such as stomatal closure, gene expression, and the accumulation of osmoprotectants and stress proteins. ABA transporters function as the first step for propagating synthesized ABA. To prevent water loss, ABA influx in guard cells is detected by several protein kinases, such as SnRK2s and MAPKs that regulate stomatal closure. ABA mediates a wide variety of gene expression machineries with stress-responsive transcription factors, including DREBs and AREBs, to acquire drought stress resistance in whole tissues. In this chapter, we summarize recent advances in drought stress signaling, focusing on gene networks in cellular and intercellular stress responses and drought resistance.