Plant responses to auxin and phosphate (Pi) starvation are closely linked. However, the underlying mechanisms connecting auxin to phosphate starvation (−Pi) responses are largely unclear. Here, we show that OsARF16, an auxin response factor, functions in both auxin and −Pi responses in rice (Oryza sativa L.). The knockout of OsARF16 led to primary roots (PR), lateral roots (LR) and root hair losing sensitivity to auxin and −Pi response. OsARF16 expression and OsARF16::GUS staining in PR and LR of rice Nipponbare (NIP) were induced by indole acetic acid and −Pi treatments. In −Pi conditions, the shoot biomass of osarf16 was slightly reduced, and neither root growth nor iron content was induced, indicating that the knockout of OsARF16 led to loss of response to Pi deficiency in rice. Six phosphate starvation-induced genes (PSIs) were less induced by −Pi in osarf16 and these trends were similar to a knockdown mutant of OsPHR2 or AtPHR1, which was a key regulator under −Pi. These data first reveal the biological function of OsARF16, provide novel evidence of a linkage between auxin and −Pi responses and facilitate the development of new strategies for the efficient utilization of Pi in rice.