Two possible indicators of a deficient segregation of functional networks are within-underconnectivity and between-overconnectivity. Both these processes can be observed in Autism Spectrum Disorder (ASD) to be associated with different core and co-occurring atypicalties of behavior. We focused on within- and between-network connectivity of Frontoparietal and Sensorimotor networks in ASD compared to typically developed (TD) peers and its links to social difficulties and impairments of executive and motor functions. To our knowledge, this study for the first time described between-network connectivity of Frontoparietal and Sensorimotor networks in ASD with relations to symptoms of ASD. In this study, we utilised resting-state functional MRI to investigate 121 participants with ASD and 84 TD children. We investigated between-group differences of the connectivity between Frontoparietal and Sensorimotor regions. We also conducted brain-behavior analysis for beta values of these connections and behavioral scores. Controlling for age and sex, we found a significant group difference within- Frontoparietal network (right and left posterior parietal cortices were underconnected in ASD) and between-networks (right posterior parietal and right lateral sensorimotor cortices were overconnected in ASD). In the ASD group, we also showed that within-Frontoparietal underconnectivity was related to lower scores of social and executive functions as well as between-networks overconnectivity was associated with social difficulties only. There were no significant relationships between scores of motor functions and beta values. We confirmed the hypothesis of deficient segregation for Frontoparietal and Sensorimotor networks in ASD. These findings highlight the importance of between-network connectivity investigation.