In this study we examined the prospective relationships between perseverative thoughts, internalizing negative emotions, and somatic complaints in children aged 9-13, and evaluated whether a perseverative thoughts intervention had a beneficial effect on these experiences. Children (N=227) from 7 primary schools in Leiden, the Netherlands, recorded their perseverative thoughts during one week, 138 of whom were instructed to postpone these thoughts to a special 30min period in the early evening. Children who had received the postponement instructions showed a reduction in the frequency of perseverative thoughts, and girls also in the duration of them. Girl's perseverative thoughts were positively associated with the number of somatic complaints and with negative emotions. The postponement intervention also seemed to reduce somatic complaints in the seventh grade children. These findings confirm the previously found prospective relationship between perseverative thoughts and children's well-being and provide initial validation for the use of the postponement intervention to reduce perseverative thoughts in this age group, particularly for girls.