Despite　a　rich　tradition　in　studying　contract-trust　nexus,　the　mutual　relationship　between　these　two　modes　of　governance　remains　equivocal.　Adopting　a　dual-functional　and　relationship-phase-contingent　view　of　contracts,　we　theorize　that　firms＇　perception　of　the　chief　function　of　contracts　varies　throughout　the　relationship　life　cycle,　which　results　in　a　relationship-phase-contingent　contract-trust　nexus.　We　tested　our　hypotheses　with　data　collected　from　the　supplier-retailer　dyads　using　quasi-longitudinal　analysis.　The　results　indicate　that　contracts　substitute　goodwill　trust　in　the　exploration　phase　because　of　the　significantly　negative　effect　of　the　safeguarding　function,　whereas　in　the　expansion　phase,　contracts　complement　goodwill　trust　because　the　positive　effect　of　the　coordination　function　dominates.　In　the　maturity　phase,　because　the　effects　of　the　two　functions　on　goodwill　trust　are　both　significant,　with　neither　of　them　dominating　the　total　effect,　the　net　effect　of　contracts　on　goodwill　trust　becomes　insignificant.　Overall,　we　provide　new　insights　into　when　and　how　contracts　complement　or　substitute　goodwill　trust　throughout　the　relationship　life　cycle.