Entrepreneurial ecosystems (EEs) are interconnected networks fostering innovation and growth. Professional Services Firms (PSFs) - legal, accounting, consulting, finance - are vital yet underexplored within EEs, reducing information gaps and offering expertise. This study examines PSFs' role in West African EEs (Nigeria, Ghana, Senegal) compared to Silicon Valley, Bangalore, Berlin. Mixed methods (30 interviews, 200 surveys, cross-case analysis) show PSFs as key intermediaries bridging resource gaps, enabling networks, and navigating fintech/ agritech regulations. Findings: West African PSFs...