Abstarct: The validity of research findings has always been a debatable issue in educational research, in general, and ELT research, in particular. Such an important issue has been more controversial especially when it came to experimental or quasi-experimental design in ELT research. Bearing this in mind, the researcher set to investigate the construct, external and internal validity criteria as defined in the primary sources of research in 40 papers published in Iranian (n = 20) and non-Iranian (n = 20) journals in ELT domain. The sample was randomly chosen from the body of papers including experimental or quasi-experimental design published from 2010 to 2020. Adopting an exploratory approach to the sample, they were meticulously analyzed in terms of their observing the threats to construct, external and internal validity. Having extracted the frequencies of the criteria, chi-square goodness of fit test and chi-square independence test were used to analyze the data. The results showed that the papers were generally deviant from the ideal state of observing construct, external and internal validity threats. In addition, a further comparison of the papers published in all journals indicated that among the measured internal validity threats, instrumentation was the less frequent threat followed by selection bias, history, maturation, diffusion and testing effect and selection-maturation interaction, regression, mortality, experimenter-subject effect were the less important ones, and the papers generally failed to meet the criteria, namely, setting-treatment interaction, pretest-treatment interaction and then selection-treatment interaction and subject-experimenter effect in the sample papers as the threats to external validity. Implications of the study for academicians were also discussed in accordance with the findings of the study.