Legislators play a key role in determining trade policy. In many countries, parliaments have to authorize their government to commence a trade negotiation and in most countries, parliaments must ratify any agreement before it enters into force. Unsurprisingly, most trade agreements are ratified along party lines but in some instances, defectors from the government prevent an agreement from entering into force. What drives these rebels? In this paper, I argue that material interests of the constituencies of lawmakers are the main reason for them to rebel from the party line. The more a legislator’s constituents stand to lose economically from an agreement, the more likely is this legislator to defect from her party if her party is in favor of the agreement and vice versa for legislators from districts that stand to benefit from trade liberalization. To test this hypothesis, I analyze 11,636 votes from twelve countries on the ratification of 53 different trade agreements. The results support the hypothesis and also demonstrate that the effect of the material interest on legislators' likelihood to rebel depends on the scope and depth of the trade agreement. This paper has implications for research on trade policy-making, representation, and legislator behavior.