Women-owned-or-led small and medium enterprises (WSMEs) are underrepresented in public and corporate supply chains worldwide. There is growing interest in promot- ing supplier diversification and SMEs’ integration into value chains, but limited causal evidence whether interventions to support WSMEs’ participation in procurement are effective. This paper conducts a phased randomized controlled trial to estimate the impacts of corporate procurement training for WSMEs in Colombia. The program in- creases procurement knowledge and readiness, resulting in a 10 percentage point (p.p.) increase in registrations to corporate portals and an 8 p.p. increase in the likelihood of submitting a bid. Impacts on winning bids are concentrated on WSMEs with prior pro- curement knowledge or experience, whose probability of winning a contract increases by 8 to 9 p.p. These impacts are approximately 20% of the control means. More broadly, the paper illustrates how complier-weighted treatment effects can be used to evaluate programs delivered through a funnel-shaped participation processes, common in private sector development interventions.