Cardiovascular diseases, one of the leading causes of mortality, are suffered by male subjects more frequently than female ones. Cluster of differentiation-40 molecule (CD40) is a receptor on the cell surface that is included in TNF family. It is reported that ligation of CD40 on endothelial cells by CD40L of platelets will stimulate endothelial cells and lead to the increase of endothelial ICAM-1 expression. To examine the influence of testosterone to the expression of CD40 in normoglycemic endothelial cells, we had done an in vitro laboratory study using post test only control group design. Study subject was the primary culture of human umbilical vein endothelial cells (HUVEC). Independent variables were testosterone that was given in 3 doses: 1 nM, 10 nM, and 100 nM. Normo glucose environment was given in 5.6 mM. The expression of endothelial CD40 was measured using enzyme-linked immunosorbent assay (ELISA). Using (multiple) independent t-test it was revealed that CD40 expression in the endothelial cells (EC) without testosterone (T) (15.68 ± 5.81 pg/ml) was not significantly different with those treated with 1 nM T (19.26 ± 2.01 pg/ml; p = 0.496), 10 nM T (18.78 ± 2.7 pg/ml; p = 0.57), and 100 nM T (18.35 ± 0.2 pg/ml; p = 0.582). There was a trend of inverse relationship between the dose of T and the expression of CD40 in the EC, however, using one-way ANOVA it was revealed that the exposure of T in incremental doses did not significantly influence endothelial CD40 expression (p = 0.73). It can be concluded that testosterone does not influence the expression of CD40 in normal endothelial cells.