Despite the recent theoretical and empirical interest in understanding teachers' motivation to conduct research, there is an absence of an appropriate quantitative instrument to measure it. Thus, drawing on an argument-based approach to validation, Deemer, Martens, and Buboltz's (2010) Research Motivation Scale (RMS) was adapted and a network of empirical evidence was established in 2 separate studies with 202 and 201 Iranian school English teachers (SETs) to construct such an instrument. We interpreted our findings across 4 inferences (i.e., target domain, scoring, generalization, and extrapolation), judging if the evidence supported our proposed interpretation of the scores. The overall process resulted in the 22-item Teacher Research Motivation Scale (TRMS) with 3 dimensions, namely Intrinsic Research Motivation (IRM), Extrinsic Research Motivation (ERM), and Research Failure Avoidance (RFA), offering preliminary support for the interpretation of the TRMS scores as a measure of Iranian SETs' motivation to conduct research. Potential implications and suggestions for future research are discussed.