This study demonstrates the feasibility of free-standing conductive polymer nanosheets (referred to hereafter as “conductive nanosheets”) as bioelectrodes for plant leaves. The conductive nanosheet exhibited ultra-conformability and physical adhesion to unevenly structured surfaces, such as the veins of a plant leaf, without the use of chemical glue, owing to the ultra-thin and light structure (300 nm thick, 150 µg). The conductive nanosheet coupled with a Bluetooth system enabled wireless biopotential measurement of plant leaves (Angelica keiskeiKoidzumi) up to approximately 1500 h, while conventional bioelectrodes such as pre-gel electrodes caused discoloration during the measurement, owing to the acrylic glue utilized for adhesion. We also discovered that the biopotential pattern was altered under periodic light-emitting diode (LED) irradiation. Such minimally invasive measurements using the conductive nanosheets can pave the way for a revolutionary method to analyze the bioactivity of plants in the application of agriculture and food science.Free-standing conductive polymeric nanosheets consisting of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) and polystyrene-block-polybutadiene-block-polystyrene layers were fabricated by roll-to-roll processing method. The conductive nanosheets were used as “nanosheet electrodes” for the biopotential measurement of plant leaves, which realized minimally invasive biopotential measurement of plant leaves.