Cilia and flagella play critical roles in cell motility, development and sensory perception in animals. Formation and maintenance of cilia require a conserved protein transport system called intraflagellar transport (IFT). Here, we show that Caenorhabditis elegans dyf-11 encodes an evolutionarily conserved protein required for cilium biogenesis. dyf-11 is expressed in most of the ciliated neurons and is regulated by DAF-19, a crucial transcription factor for ciliary genes in C. elegans. dyf-11 mutants exhibit stunted cilia, fluorescent dye-filling defects (Dyf) of sensory neurons, and abnormal chemotaxis (Che). Cell- and stage-specific rescue experiments indicated that DYF-11 is required for formation and maintenance of sensory cilia in cell-autonomous manner. Fluorescent protein-tagged DYF-11 localizes to cilia and moves antero- and retrogradely via IFT. Analysis of DYF-11 movement in bbs mutants further suggested that DYF-11 is likely associated with IFT complex B. Domain analysis using DYF-11 deletion constructs revealed that the coiled-coil region is required for proper localization and ciliogenesis. We further show that Traf3ip1/MIP-T3, the mammalian orthologue of DYF-11, localizes to cilia in the MDCK renal epithelial cells.