Conduct disorder (CD) is a serious behavioral disorder of childhood and adolescence. The default mode network (DMN) is a brain network which supports self-referential cognitive processes and is typically deactivated during task performance. The aim of this study was to investigate DMN connectivity in male adolescents with pure CD compared to typically-developing controls. Eighteen male adolescents with CD and 18 sex-, age- and education-matched typically-developing (TD) participants were recruited. Current and lifetime psychiatric disorders were assessed using the Chinese version of the Schedule for Affective Disorder and Schizophrenia for School-Age Children-Present and Lifetime Version. Resting state functional magnetic resonance imaging (fMRI) data were obtained using a 3.0 T scanner. Independent components analysis (ICA) was used to investigate functional connectivity between the DMN and related brain regions. DMN activity was observed in medial prefrontal, posterior cingulate, and lateral parietal cortices, and extended to the brainstem. Adolescents with CD showed significantly reduced functional connectivity within the bilateral posterior cingulate cortex (PCC), bilateral precuneus and right superior temporal gyrus relative to TD controls. CD is associated with reduced functional connectivity within the DMN and between the DMN and other regions. These preliminary results suggest that deficits in DMN functional connectivity may serve as a biomarker of CD.