Background: We analyze trends in bullying victimization prevalence in a representative sample of Spanish adolescent schoolchildren in 2006, 2010, and 2014. Methods: We distinguish between reported bullying, which is assessed via the global question in the Revised Bully/Victim Questionnaire by Olweus, and observed bullying, which is a measure developed from the answers that the adolescents gave to specific items that refer to different types of bullying that have been codified as physical, verbal, and relational bullying. Results: For 2006 and 2010/2014, the results show stability in the assessment of reported bullying and an increase in observed bullying, analyzed both globally and within the 3 categories: physical, verbal, and relational. Conclusions: A valid, reliable, and accurate measure to detect cases of bullying is necessary, as is the importance of continuing efforts devoted to raising awareness and the prevention of this phenomenon.