Adenosine deaminases acting on RNA (ADARs) are the primary factors underlying adenosine to inosine (A-to-I) editing in metazoans. Here we report the first global study of ADAR1-RNA interaction in human cells using CLIP-seq. A large number of CLIP sites are observed in Alu repeats, consistent with ADAR1' s function in RNA editing. Surprisingly, thousands of other CLIP sites are located in non-Alu regions, revealing functional and biophysical targets of ADAR1 in the regulation of alternative 3â €2 UTR usage and miRNA biogenesis. We observe that binding of ADAR1 to 3â €2 UTRs precludes binding by other factors, causing 3â €2 UTR lengthening. Similarly, ADAR1 interacts with DROSHA and DGCR8 in the nucleus and possibly out-competes DGCR8 in primary miRNA binding, which enhances mature miRNA expression. These functions are dependent on ADAR1' s editing activity, at least for a subset of targets. Our study unfolds a broad landscape of the functional roles of ADAR1.