In this work, a compact, mobile phone-based ECL sensor apparatus was developed using the phone cameras, screen-printed electrodes (SPE), and mobile app for dopamine detection. Methods of DC voltage application for ECL reaction were comprehensively studied from the mobile phone itself or external power. Under optimized sensing conditions, with disposable carbon SPE and 20 mM coreactant tri-n-propylamine (TPrA), acceptable repeatability and reproducibility were achieved in terms of relative standard deviation (RSD) of intra- and interassays, which were 6.7 and 5.5%, respectively. The biochemical compound dopamine was measured due to its ECL quenching characteristics and its clinical importance. The quenching mechanism of Ru(bpy)32+/TPrA by dopamine was investigated based on the estimation of the constants of the Stern-Volmer equations. The linear range for detectable dopamine concentration was from 1.0 to 50 μM (R2 = 0.982). As the developed mobile phone-based ECL sensor is simple, small and assembled from low-cost components, it offers new opportunities for the development of inexpensive analytical methods and compact sensors.