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.