Assessments of functional connectivity of resting state and task-based networks using independent component analysis (ICA) in this population may help describe long-term effects of childhood brain tumors and adjuvant treatments in hopes of identifying potential neuronal markers that may aid in prognosis and inform innovative interventions to optimize outcomes. The present study used ICA to evaluate presence and strength of functional connectivity networks in 23 adult survivors of childhood posterior fossa tumors (9 low grade, 14 high grade) at least 5 years past diagnosis compared to 40 age- and sex-matched healthy peers. Across groups, functional connectivity networks and their task-related engagement during attention and working memory tasks were assessed, and relationships between task-based connectivity and cognitive task performance were evaluated. Resting state functionally connected networks were also extracted and evaluated for any group differences in recruitment patterns. High grade tumor survivors performed more poorly than their low grade tumor survivor or healthy peers on most attention and working memory measures. Task-based components demonstrated general trends in which default mode network (DMN) component recruitment decreased in task-relatedness with higher task load while cognitive network component recruitment increased. Low grade survivors showed distinct patterns in DMN component recruitment, and high grade survivors demonstrated limited recruitment of an executive control network component at higher task loads. Correlations between task relatedness and task performance did not survive correction but demonstrated different trends of interest across groups. Resting state components emerged with some overlap with task components, but group differences were not observed. Results reflect differences in functional network recruitment across long-term survivors of high grade and low grade brain tumors such that low grade tumor survivors may demonstrate more compensatory functions, while high grade tumor survivors may develop some compensatory functions alongside recruitment of other networks that do not improve performance. Findings also indicate the importance of cognitive intervention in both survivor groups and the necessity to track low grade tumor survivors despite their cognitive abilities often resembling that of their healthy peers.