We study the phenomenology of the Georgi-Machacek model at next-to-leading order in QCD matched to a parton shower, using a fully automated tool chain based on MadGraph5_aMC@NLO and FeynRules. We focus on the production of the fermiophobic custodial fiveplet scalars H05, H±5, and H±±5 through vector boson fusion (VBF), associated production with a vector boson (VH5), and scalar pair production (H5H5). For these production mechanisms we compute next-to-leading order corrections to production rates as well as to differential distributions. Our results demonstrate that the Standard Model overall K-factors for such processes cannot in general be directly applied to beyond-the-Standard-Model distributions, due both to differences in the scalar electroweak charges and to the variation of the K-factors over the differential distributions.