Three studies (1 correlational and 2 experiments) applied the investment model to explain social network approval for others’ romantic relationships. Study 1 supported the prediction that friends’ perceived satisfaction and perceived alternatives were predictive of their approval for target relationships, while perceived investments was not a significant predictor. Studies 2 and 3 employed experimental manipulations of perceived satisfaction to test its causal impact on relationship approval, and in these studies, perceived satisfaction was a significant predictor of relationship approval. Taken as a whole, these findings supported the prediction that perceived relationship satisfaction is a causal factor influencing friends’ approval of target romantic relationships.