Intraflagellar transport (IFT) is a highly conserved mechanism for motor-driven transport of cargo inside cilia. However, the mechanism of selective transport of cargo to cilia and entry across the diffusion barrier is not well understood. WDR35/IFT121 is a component of the IFT-A complex, best known for ciliary retrograde transport. Small Wdr35 mutant cilia are formed but fail to enrich in diverse classes of ciliary membrane proteins. Whilst the assembly of the IFT-B complex is unaffected, these exhibit retrograde trafficking defects in Wdr35 mutants. In contrast, the IFT-A peripheral components are degraded and core components remain stuck at the cilia base. The deep sequence homology and structural similarity of WDR35 and other IFT-As to the coatomer COPI proteins α and ß’, and accumulation of electron-light vesicles around Wdr35 mutant cilia, suggest that WDR35 is required to form coated vesicles delivering cargo from the Golgi necessary for cilia elongation. This is the first insitu proof towards a novel coatomer function for WDR35 and likely other IFT-A proteins in transporting ciliary membrane proteins from the Golgi.