The aim of this study was to report an inter-observer agreement in proximal caries detection from digital bitewing radiographs viewed and evaluated on a smartphone display. A total of 200 proximal surfacesfrom digital bitewing radiographs stored in the Picture Archiving and Communication System (PACS) of Chulalongkorn University dental hospital were selected. Images of selected radiographs were exported in JPEG format and transferred to an iPhone 8 plus. Each proximal surface was viewed and evaluated by seven observers in a dimly lit room (ambient light intensity < 100 lux). The ratings were on a 5-point-scale. Weighted kappa test was used to determine agreement among observers. Inter-observer agreement among observers ranged from moderate to almost perfect (0.47 - 0.82). Images of digital bitewing radiographs viewed on a smartphone provided an acceptable result in terms of consistency between dentists and may be considered one of the methods used for proximal caries detection.