Associative theories of creativity posit that high-creativity individuals possess flexible semantic memory structures that allow broad access to varied information. However, the semantic memory structure characteristics and neural substrates of creative writing are unclear. Here, we explored the semantic network (SN) features and the predictive whole-brain functional connectivity (FC) associated with creative writing and generated mediation models. Participants completed two creative story continuation tasks. We found that keywords from written texts with superior creative writing performance were highly interconnected, and encompassed more semantic categories. Connectome predictive modeling (CPM) was conducted with resting-state (rs) functional magnetic resonance imaging (fMRI) data to identify whole-brain functional connectivity (FC) patterns related to creative writing. FC was found to mediate the relationship of creative writing and SN features. These results highlight how semantic memory structure and the internal thought-oriented brain functional connectivity pattern support creative writing performance. Our findings extend prior research on the role of semantic memory structure and the default mode network (DMN) in creativity, expand upon previous research on semantic creativity, and provide insight into the cognitive and neural foundations of creative writing.