Ordering effect on the performance of Ga0.5In0.5P visible light-emitting diodes (LEDs) has been reported. The GaInP LEDs were fabricated on GaAs substrates at 675 and 730°C by metalorganic chemical vapor deposition, with ordered and disordered structures. A sample with an ordered structure shows anomalous device performance, where emitting wavelength change, low light intensity, and early saturation were observed from the current-light intensity relationship. From the current-voltage measurement, it was found that the sample with ordered structure also yields an inferior diode performance. These phenomena could be due to the existence of antiphase boundaries in the ordered structures. The antiphase boundaries can act as generation-recombination centers and result in the anomalous behavior of the ordered GaInP LED.