The exploitation of AuxRh1−x alloy nanocrystals for specifically and directly identifying carbamate pesticides is reported for the first time and could be easily further developed to meet the specific needs of emergency intoxication cases. In this study, AuxRh1−x alloy nanocrystals with a tunable composition were synthesized and then employed for the electrocatalytic oxidation of carbamate pesticides. Compared with other AuxRh1−x samples and monometallic analogues, the Au42Rh58 sample with an optimized composition showed advances in terms of its electrocatalytic activity. According to electrochemical assessments, we discovered that the Au42Rh58 sample had specific responses to carbaryl. Typical common existing substances including glucide, amino acids, metal ions, and OP pesticides showed no interference in carbaryl determination. Moreover, Au42Rh58 nanocrystals displayed a considerable response towards 1 nM carbaryl without the assistance of acetylcholinesterase (AChE), cholinesterase (ChE) or other biochemical recognition elements. The observed high-efficiency detection was driven by electrocatalyzing the hydrolysis product of carbaryl in a strong alkaline solution. Au42Rh58 alloy nanocrystals with high catalytic activity and good selectivity are promising sensing materials for the detection of trace levels of carbaryl. Furthermore, Au42Rh58 alloy nanocrystals with uniform shape and narrow size distribution could be used in micro/nanoelectrode fabrication technology such as in screen-printing or ink-jetting or in the further design and implementation of real-time identification systems.