The endangered Devils Hole pupfish, Cyprinodon diabolis, lives in a single warm-pool of unknown depth within Death Valley National Park, California/Nevada. Over the past several years, C. diabolis has reached record-low numbers, spurring renewed conservation and recovery efforts. Though factors that influence spawning may be important in regulating C. diabolis population size, much is still unknown about the reproductive ecology of this notoriously difficult-to-breed species. Over 11 months, February–December 2010, we monitored spawning behavior of C. diabolis and associated environmental conditions within Devils Hole. A solar-powered video surveillance system, incorporating above-water and underwater cameras, provided continuous monitoring of the shallow spawning shelf. We additionally monitored spawning activity during biweekly in-person surveys. Datalogging meters continuously recorded dissolved oxygen, temperature, and lux; monthly in-person surveys recorded time-lapse algal and substrate cover. Comparison of data from the three different survey methods we employed has shown superior efficacy of the underwater camera in monitoring C. diabolis spawning activity. Based on data from the underwater camera, primary spawning season takes place in the spring, March–May, and a secondary spawning season takes place in the fall, October–November. Regression models have thus far identified algal cover and daily light energy input to the system as main factors in C. diabolis spawning activity. The results from this study will be provided to NPS and USFWS managers to help design C. diabolis captive breeding programs, as well as information on how current technologies might be more broadly applied to monitor other aquatic species.