"Visible upconversion emission of Er3+ in nanocrystalline BaZrO3 (BZO) powder is obtained under IR excitation in the range between 900 to 1050 nm. In single Er3+ doped BaZrO3 the blue emission was neglected and when Yb3+ is added then it acts as a sensitizer. The BZO was prepared by a hydrothermal process at low temperature (100◦C). The synthesized nanocrystalline cubic perovskite phase remains stable under subsequent annealing treatment up to 1000◦C. Additional or different crystalline phases or segregation were not detected. Green and red emissions of Er3+ are enhanced in the codoped samples of Yb3+ − Er3+ by three orders of magnitude. The blue emission dependents on both excitation power and pump wavelength. It is the first time that upconversion emission is observed in a BaZrO3 matrix. A possible mechanism for the UV to red emission under NIR excitation is discussed based on experimental results."