We propose an ultracold atom analog of false-vacuum decay using all three states of a spin-1 Bose gas. We consider a one-dimensional system with both radio-frequency and optical Raman couplings between internal states. An advantage of our proposal is the lack of a time-modulated coupling, which can lead to instabilities. Within the elaborate phase structure of the system, we identify an effective Klein-Gordon field and use Gross-Pitaevskii simulations within the truncated Wigner approximation to model the decay of a metastable state. We examine the dependence of the rate of vacuum decay on particle density for 7Li and 41K and find reasonable agreement with instanton methods.