Major, minor, and trace element data, as well as backscattered electron images, were collected for clinopyroxene crystals in alkaline silicate rocks (phonolite, tephriphonolite, latite, phonotephrite, and pyroxenite) of the Bear Lodge and Mineral Hill alkaline complexes, Wyoming. Samples of alkaline rocks thought to represent early and later stages of magmatism, based on observed intensity of alteration and cross-cutting relationships, were collected from the Bear Lodge alkaline complex (BLAC) to investigate clinopyroxene compositional trends that might be influenced by the magmatic evolution of the system and production of a carbonatite melt. Clinopyroxene crystals from jacupirangite units at the Mineral Hill alkaline complex (MHAC) were analyzed for comparison with samples from the BLAC and to test whether clinopyroxene chemistry might be influenced by possible carbonatite magmatism. Elemental analyses were conducted at Washington State University’s GeoAnalytical Lab using a JEOL JXA-8500f field emission electron microprobe (EPMA). Minor and trace element concentrations were determined by laser ablation inductively coupled mass spectrometry (LA-ICP-MS) using a New Wave UP-213 laser ablation system coupled with an Agilent 7700 quadrupole ICP-MS at Washington State University’s GeoAnalytical Lab. Whole rock multi-element data for most samples can be found in the following data releases. Verplanck, P.L., Andersen, A.K., and Van Gosen, B.S., 2020, Whole-rock geochemical data for the Bear Lodge alkaline complex, Wyoming: 2009 - 2013: U.S. Geological Survey data release, https://doi.org/10.5066/P9RCPAMC. Andersen, A.K., Olinger, D.A., Navarra, A.M., and Howard, C.K., 2021, Lithogeochemistry and images of selected drill core samples from the Mineral Hill alkaline complex, Wyoming: U.S. Geological Survey data release, https://doi.org/10.5066/P94E59KF.