Here we report a novel peptide–polysaccharide hybrid hydrogel as a potential carrier for sustained delivery of hydrophobic drugs. The hybrid hydrogel composed of Fmoc-diphenylalanine (Fmoc-FF) peptide and konjac glucomannan (KGM) was prepared through molecular self-assembly of Fmoc-FF in the KGM solution. The physicchemical properties of the Fmoc-FF–KGM hybrid hydrogel were further evaluated. This hybrid hydrogel exhibited a highly hydrated, rigid and nanofibrous gel network in which self-assembled peptide nanofibers were interwoven with the KGM chains. The results of a stability test and rheology study showed that the hybrid hydrogel has much higher stability and mechanical strength compared to Fmoc-FF hydrogel alone. Both CD and FTIR analysis indicated an anti-parallel β-sheet arrangement of Fmoc-FF peptide in self-assembled nanofibers, regardless the presence of KGM. Moreover, docetaxel was chosen as a model of hydrophobic drugs and incorporated into hydrogels to study the in vitro release behavior. The sustained and controlled drug release from this hybrid hydrogel was achieved by varying the KGM concentration, molecular weight, aging time or β-mannanase concentration. Our results not only provide a new strategy for fabricating Fmoc-FF–KGM hybrid hydrogel as a sustained-release drug carrier but also open an avenue for the design of new self-assembling peptide–polysaccharide hybrid hydrogels.