Abstract: Wide-field fluorescent imaging on a mobile device having a camera is accomplished with a compact, light-weight and inexpensive optical components that are mechanically secured to the mobile device in a removable housing. Battery powered light-emitting diodes (LEDs) contained in the housing pump the sample of interest from the side using butt-coupling, where the pump light is guided within the sample holder to uniformly excite the specimen. The fluorescent emission from the sample is then imaged using an additional lens that is positioned adjacent to the existing lens of the mobile device. A color filter is sufficient to create the dark-field background required for fluorescent imaging, without the need for expensive thin-film interference filters.