This paper assesses the stages and findings of a mass movement monitoring system developed for continuous long-term monitoring applications using optical fiber cable as a sensor to decrease the risks associated with slope instabilities. During this study, a system composed of optical fiber cables and a device referred to as the Brillouin Optical Time Domain Analyzer (BOTDA) has been used. This system has been implemented in a risky landslide area in the Bahcecik region of Kocaeli, one of the active landslide-prone regions in the Marmara region, Turkey. The strain data have enabled investigating the effects of precipitation, groundwater level fluctuation, and temperature change on mass movement for a period of 6 months. The evaluation of the data revealed that the change in strain was directly proportional to precipitation, groundwater head, and temperature difference. The mass movement characteristics that were validated by periodical surface topography monitoring measurements have shown that the variation of the relative displacements was in good agreement with the displacements estimated by the optical fiber system. These results showed that the system gave reliable results regarding the suitability of the utilized cable for mass movement monitoring. Since this study is the first study performed ever in Turkey that has used optical fibers for mass movement assessment, the results discussed in this paper are expected to guide slope monitoring and early warning system applications. It is anticipated that the system will also contribute significantly to understanding the impact of precipitation, groundwater level, and temperature changes on mass movement.