The primary cilium organizes Hedgehog signaling and shapes embryonic development, and its dysregulation is the unifying cause of ciliopathies. We conducted a functional genomic screen for Hedgehog signaling by engineering antibiotic-based selection of Hedgehog-responsive cells and applying genome-wide CRISPR-mediated gene disruption. The screen robustly identifies factors required for ciliary signaling with few false positives or false negatives. Characterization of hit genes uncovers novel components of several ciliary structures, including a protein complex containing δ- and ε-tubulin that is required for centriole maintenance. The screen also provides an unbiased tool for classifying ciliopathies and reveals that many congenital heart disorders are caused by loss of ciliary signaling. Collectively, our study enables a systematic analysis of ciliary function and of ciliopathies and also defines a versatile platform for dissecting signaling pathways through CRISPR-based screening.