Developmental dyslexia (DD) is an unexpected failure to learn to read despite otherwise favorable conditions in school-aged children. The theta rhythm of the electroencephalogram (EEG) has been related to several cognitive processes and may therefore be related to DD. The aims of this study were to (i) compare the theta relative power (TRP) while reading in children with DD versus controls, (ii) determine whether TRP while reading correlates with school performance, and (iii) compare the lateralization of TRP between children with DD and controls. Children with DD were recruited from a clinic at a third-level institution. EEG were performed under standard conditions and while children were reading. In children with DD, mean TRP scores while reading were higher in the frontal regions mainly of the right hemisphere. There were several negative correlations between academic scores (overall, Spanish, mathematics) and TRP for all EEG electrode locations. There were no differences in TRP laterality between the DD and control groups. In conclusion, the higher TRP in frontal regions may relate to compensatory effort in attention and working memory, while the negative correlations between academic performance and TRP may suggest deficiencies in voluntary attention and phonological working memory in these patients.