Background Targeted temperature management (TTM) for out-of-hospital cardiac arrest is associated with improved functional survival and is a class I recommendation in resuscitation guidelines. However, patterns of utilization of TTM and adherence to recommended TTM guidelines in contemporary practice are unknown. Methods and Results In a multicenter, prospective cohort of consecutive adults with non-traumatic out-of-hospital cardiac arrest in the Resuscitation Outcomes Consortium in 2012 to 2015, we identified all adults (≥18 years) who were potential candidates for TTM. Of 37 898 out-of-hospital cardiac arrest patients at 186 hospitals across 10 Resuscitation Outcomes Consortium sites, 8313 survived for ≥4 hours after hospital arrival, of which, 2878 (34.6%) received TTM. Mean age was 61.5 years and 36.3% were women. Median hospital rate of TTM use was 27% (interquartile range [IQR]: 14%, 45%), with an over 2-fold difference across sites after accounting for differences in presentation characteristics (median odds ratio, 2.10 [1.83-2.26]). Notably, TTM utilization decreased during the study period (57.5%  to 26.5% , P<0.001) including among shockable out-of-hospital cardiac arrest (73.4% to 46.3%, P<0.001). When administered, the median rate of deviation from one or more recommended practices was 60% (IQR: 40%, 78%). The median rate for delayed onset of TTM was 13% (IQR: 0%, 25%), varying by 70% for identical patients across 2 randomly chosen hospitals (median odds ratio 1.70 [1.39-1.97]). Similarly, the median rate for TTM <24 hours was 20% (IQR: 0%, 34%) and for achieved temperature <32°C was 18% (IQR: 0%, 39%), with marked variation across sites (median odds ratios of 1.44 [1.18-1.64] and 1.98 [1.62-2.31], respectively). Conclusions There has been a substantial decline in the utilization of TTM with significant variation in its real-world implementation. Further standardization of contemporary post-resuscitation practices, like TTM, is critical to ensure that their potential survival benefit is realized.