Background/Objective: In recent years, the use of electronic communication devices at early ages has become widespread, promoting concern about the possible risks associated with technology use. This research explores the connection between being a victim of online aggression, and anxiety and low self-esteem by analysing: 1) the level and developmental trajectory of anxiety and self-esteem; 2) the effect of anxiety and self-esteem in 4th and 5th grade of Primary Education on cyber-victimization in 6th grade, both directly and mediated by risk internet behaviours; and 3) the effect of cyber-victimization in 6th grade on anxiety and self-esteem in that same year. Method: A three-year longitudinal study was undertaken with 268 students attending nine schools in Asturias (Spain). Participants completed measures at three timepoints, separated by a year interval: when they were in 4th, 5th, and 6th grade. In 4th and 5th grade, self-report scales of anxiety and self-esteem were administered. In 6th grade, self-report scales of risk internet behaviors and cyber-victimization were also administered. Results: An increase in anxiety and a decrease in self-esteem from 5th to 6th grade was found. There was also an indirect effect of anxiety and self-esteem in 5th grade on cyber-victimization in 6th grade, mediated by risk internet behaviors. Cyber-victimization in 6th grade negatively impacted anxiety and self-esteem in that same year. Conclusions: The results obtained in this work suggest a bidirectional relationship between anxiety/low self-esteem and cyber-victimization. Antecedentes/Objetivo: En los & uacute;ltimos a & ntilde;os se ha generalizado el uso de dispositivos electr & oacute;nicos de comunicaci & oacute;n en edades tempranas, aumentando la preocupaci & oacute;n por los posibles riesgos asociados. Esta investigaci & oacute;n explora la relaci & oacute;n entre ser v & iacute;ctima de ciberagresiones, la ansiedad y la baja autoestima, analizando: 1) el nivel y trayectoria evolutiva de la ansiedad y la autoestima, 2) el efecto de la ansiedad y la autoestima en 4 degrees y 5 degrees de Educaci & oacute;n Primaria sobre la cibervictimizaci & oacute;n en 6 degrees, tanto directo como mediado por las conductas de riesgo en internet, y 3) el efecto de la cibervictimizaci & oacute;n en 6 degrees sobre la ansiedad y la autoestima ese mismo a & ntilde;o. M & eacute;todo: Se realiz & oacute; un estudio longitudinal de tres a & ntilde;os con 268 alumnos de nueve escuelas en Asturias (Espa & ntilde;a). Se les aplicaron los instrumentos en tres momentos, separados por un intervalo de un a & ntilde;o: cuando estaban en 4 degrees, 5 degrees y 6 degrees de Primaria. En 4 degrees y 5 degrees se administraron cuestionarios de autoinforme de ansiedad y autoestima y en 6 degrees se administraron adem & aacute;s cuestionarios de autoinforme de conductas de riesgo en internet y cibervictimizaci & oacute;n. Resultados: Se encontr & oacute; un aumento de la ansiedad y una disminuci & oacute;n de la autoestima de 5 degrees a 6 degrees curso. Tambi & eacute;n hubo un efecto indirecto de la ansiedad y la autoestima en 5 degrees sobre la cibervictimizaci & oacute;n en 6 degrees, mediado por las conductas de riesgo en internet. La cibervictimizaci & oacute;n en 6 degrees afect & oacute; negativamente a la ansiedad y la autoestima en ese a & ntilde;o. Conclusiones: Los resultados obtenidos en este trabajo indican que hay una relaci & oacute;n bidireccional entre ansiedad/baja autoestima y cibervictimizaci & oacute;n.