Avirulence effectors (Avrs), encoded by plant pathogens, can be recognized by plants harboring the corresponding resistance proteins, thereby initiating effector-triggered immunity (ETI). In susceptible plants, however, Avrs can function as effectors, facilitating infection via effector-triggered susceptibility (ETS). Mechanisms of Avr-mediated ETS remain largely unexplored. Here we report that the Magnaporthe oryzae effector Avr-PikD enters rice cells via the canonical cytoplasmic secretion pathway and suppresses rice basal defense. Avr-PikD interacts with an LSD1-like transcriptional activator AKIP30 of rice, and AKIP30 is also a positive regulator of rice immunity, whereas Avr-PikD impedes its nuclear localization and suppresses its transcriptional activity. In summary, M. oryzae delivers Avr-PikD into rice cells to facilitate ETS by inhibiting AKIP30-mediated transcriptional regulation of immune response against M. oryzae.