Abstract We have used the site-directed labeling approach to study the Ca 2+-dependent docking of factor VIIa (FVIIa) to soluble tissue factor (sTF). Nine Ca 2+ binding sites are located in FVIIa and even though their contribution to the overall binding between TF and FVIIa has been thoroughly studied, their importance for local protein–protein interactions within the complex has not been determined. Specifically we have monitored the association of the γ-carboxyglutamic acid (Gla), the first EGF-like (EGF1), and the protease domains (PD) of FVIIa to sTF. Our results revealed that complex formation between sTF and FVIIa during Ca 2+ titration is initiated upon Ca 2+ binding to EGF1, the domain containing the site of highest Ca 2+ affinity. Besides we showed that a Ca 2+-loaded Gla domain is required for an optimal association of all domains of FVIIa to sTF. Ca 2+ binding to the PD seems to be of some importance for the docking of this domain to sTF.