Bifacial c-Si photovoltaic (PV) modules can increase the performance of traditional PV modules because both sides of the cells, front and rear, absorb solar radiation. The knowledge of the temperature coefficients (TCs) is relevant to compare indoor and on-field performance of PV devices. In this paper, the TCs of c-Si bifacial PV modules from five different manufacturers were measured under natural sunlight and simulated indoor condition with a large-area steady-state solar simulator and the data were compared with the datasheet values. The effects on the TCs of an opaque and a reflective rear cover were also analyzed. There were no relevant differences between indoor and outdoor and for front and rear side TCs (within the measurement uncertainty). Slight differences with respect to the datasheet values were found for most of the modules under test for the TC for current α and for maximum power δ coefficients. However, since the manufacturers do not declare the TC uncertainty, a definitive statement cannot be made.