This paper reports, for the first time, an optical aptamer-based plant hormone sensor with a microfluidics capillary interface. The ssDNA aptamer-based sensor has better sensitivity with excellent specificity for detecting abscisic acid (ABA) than the ELISA detection kit from Sigma, indicating its potential for screening different plant hormones in a complicated matrix. Additionally, its microfluidics capillary interface allows the samples to be delivered to the sensor automatically without any external pumps, paving a way for its point-of-care application in the field.