Corruption is often the product of coordinated rule violations. Here, we investigated how such corrupt collaboration emerges and spreads when people can choose their partners versus when they cannot. Participants were assigned a partner and could increase their payoff by coordinated lying. After several interactions, they were either free to choose whether to stay with or switch their partner or forced to stay with or switch their partner. Results reveal that both dishonest and honest people exploit the freedom to choose a partner. Dishonest people seek a partner who will also lie—a “partner in crime.” Honest people, by contrast, engage in ethical free riding: They refrain from lying but also from leaving dishonest partners, taking advantage of their partners' lies. We conclude that to curb collaborative corruption, relying on people’s honesty is insufficient. Encouraging honest individuals not to engage in ethical free riding is essential.