Fresh agricultural product suppliers face severe financial constraints due to long production cycles, seasonality, and product perishability, which result in tight cash flows and limited financing options. This paper develops a three-tier supply chain game-theoretic model involving suppliers, retailers, and third-party logistics (3PL) providers. The model examines suppliers' optimal financing strategies under dual financing needs—pre-delivery financing (bank loans, retailer prepayments, and 3PL financing) and post-delivery financing (factoring)—and investigates how blockchain-based smart contracts affect supply chain efficiency and their applicability boundaries. The results reveal three key findings. First, under traditional financing modes, 3PL financing reduces the commitment friction zone, while buyer direct financing (BDF) eliminates it entirely. High-risk suppliers are better suited to bank financing, low-risk suppliers benefit more from 3PL financing, and BDF proves most advantageous for suppliers with medium liquidity risk. Second, smart contracts generate both commitment and credit gains under bank and 3PL financing, but only credit gains under BDF. Third, smart contract adoption is not universally beneficial; under low-risk conditions, they may erode 3PL profits and reduce overall supply chain performance. This study makes three contributions. It develops a novel three-tier supply chain framework incorporating both pre- and post-delivery financing interactions; it identifies the differentiated effects of smart contracts across financing structures; and it emphasizes that smart contracts are not a “one-size-fits-all” solution. These findings provide new theoretical insights and practical guidance for the design of financing strategies and blockchain-based smart contracts in fresh agricultural supply chains.