The aim of this study was to evaluate the effects of concanavalin A (CONA) on the progesterone (P4) production by bovine steroidogenic luteal cells (LCs) in vitro. Luteal cells were collected during the mid‐luteal stage (at 10–12 days following ovulation) and processed in the laboratory. Luteal cells were grown for 7 days in a humid atmosphere with 5% CO2, with or without 10% foetal bovine serum, and were subjected to the following treatments: control: no treatment; CONA (10 μg/ml); LH (100 μg/ml); CONA + LH; LH (100 μg/ml) + prostaglandin F2α (PGF2α) (10 ng/ml); CONA + LH + PGF2α. Samples of the culture media were collected on days 1 (D1) and 7 (D7) for P4 quantification. The cells were counted on D7 of culture. Differences between treatments were considered statistically significant at p < .05. Culture in the presence of CONA decreased the P4‐secreting capacity of LCs on D7 of culture, particularly in the absence of serum. The cell numbers did not change between treatments.