Despite the importance of interlanguage pragmatic rating (ILP) in the second language teaching and learning context, scant attention has been devoted to it. This study aims to investigate native EFL teachers’ major criteria in assessing the speech act of complaint produced by Iranian EFL learners. To fulfill this end, two groups of experienced native raters, including American (n=47) and British (n=30) EFL/ESL teachers, were elected for evaluating the complaint discourse completion tests (DCTs) made from video-prompts which were answered by EFL learners before. The content analysis of raters’ comments on the EFL learners’ productions revealed eleven different criteria including logical reasoning and comments, politeness, linguistic appropriacy, semantic formula, interlocutors’ relationship, register choice, formality, degree of intensity, cultural accommodations, degree of directness, and finally fluency and naturalness respectively from the most to the least frequent ones. The result of the t-test and chi-square analysis proved that British and American raters differed significantly in their degree of variations and preferences of these criteria. The results further showed that EFL learners’ responses seemed unreasonable and impolite to native raters which might be due to the different cultural norms between L1 and L2 societies and consequently encourage us to be aware of the importance of teaching sociopragmatic knowledge to the EFL learners.