In this study, hierarchical self-assembly of Au-Ag fractal patterns with bowling-alley-like hollow arrays was achieved by a hydrothermal method using L-cysteine as an environmentally friendly reducing and stabilizing reagent. Here, free thiol groups of cysteine molecules electrostatically stabilized gold and silver nanoparticles (NPs). The plasmonic resonance red-shift of Au-Ag was confirmed from self-assembled fractal patterns that consist of micro/nano fern structures forming bowling-alley-like hollow arrays. The as-synthesized large-area hierarchical self-assembly of Au-Ag fractal patterns with the synergistic catalytic advantage of a Au and Ag NPs/glassy carbon electrode (GCE) is investigated as a potential electrochemical dopamine (DA) sensor. The biosensor based on a GCE modified with bimetallic nanoparticle fractals exhibited a reversible electrochemical behavior with limits of detection and quantification of 0.014 and 0.048 mu M, respectively. Detection of DA using the developed electrochemical sensor has several advantages, such as low cost, ease-of-use, sensitivity, and stability, that can be potentially applied for detection in a variety of chemical and biosensing applications.