Nomophobia refers to the fear of not having a cell phone. In recent years, this has become a worrying phenomenon as it has been observed with increasing frequency, especially among young people. Hence, this study and its measurements using reliable and efficient instruments are important. The study aimed to determine whether the nomophobia scale of the scale of risk of addiction to social networks and Internet for adolescents (ERA-RSI), which consists of six items, would be appropriate for collecting data from a population of Mexican undergraduate students. The ERA-RSI questionnaire was originally developed in Spanish, and our target population was from México. After an initial consultation with educational experts, we decided not to alter the original scale. Its psychometric properties were explored by surveying 295 students at a Mexican public university. Additionally, techniques such as exploratory and confirmatory factor analysis, and reliability analysis were used. Descriptive statistics were computed to characterize the responses to the final instrument. The results indicated that items 3, 4, 5, and 6 formed an appropriate and reliable structure for the purposes of this study. Thus, items 1 and 2 were excluded from the analysis. Additionally, 83% of the participants obtained low to medium scores, whereas the remaining 17% exhibited high scores, indicating the need for guidance, follow-up, and attention to using technologies such as the Internet and cell phones in a balanced manner.