In this paper a novel low-cost multi-spectral optical fluorometer is presented and evaluated. The device uses a range of LEDs in the blue and violet regions of the electromagnetic spectrum and a mini-spectrometer to detect the emitted fluorescence in the UV to IR spectrum region. Custom built electronics and software were designed to control the system and the components were housed in bespoke 3D printed parts. A number of known fluorophores were tested to determine the capabilities of the fluorometer. Application of the device is demonstrated for the detection of chlorophyll a (Chl a) from laboratory grown algae and from environmental samples while analytical performance is established using both in vivo and extracted Chl a fluorescence and by comparison with a benchtop fluorometer.