The near-infrared to visible upconversion properties of nanocrystalline Gd3Ga5O12:Er3+ (1 and 5%) were studied following excitation of the 4I9/2 exited state with 800 nm radiation. Intense green and red emissions were observed from the (2H11/2, 4S3/2) → 4I15/2 and 4F9/2 → 4I15/2 transitions, respectively. The upconverted decay times in the 1% sample were identical compared to those obtained with 488 nm excitation, indicating that ESA was responsible for populating the upper emitting states. However, as the Er3+ concentration was increased to 5%, the upconverted decay times were lengthened and deviated from exponentiality, indicating the presence of energy transfer upconversion. In addition, an enhancement of the red (4F9/2 → 4I15/2) upconversion emission was observed in the 5% sample and occurred via an energy transfer process of the type (4I9/2, 4I11/2) → (4I13/2, 4F9/2).