The endowment effect has been debated for over 30 years. Recent research suggests that differential focus of attention might play a role in shaping preferences. In two studies we investigated the role of biased attention in the emergence of endowment effects. We thereby derive predictions from an extended version of evidence accumulation models by additionally assuming a bias in attentional allocation based on one’s endowment status. We test these predictions against an alternative account in which the endowment effect is the result of initial anchoring and adjustment differences (Sequential Value Matching model; Johnson & Busemeyer, 2005). In both studies we add deliberation time constraints to a standard Willingness-to-Accept/Willingness-to-Pay paradigm and consistently find that the endowment effect grows as deliberation time increases. In Study 2 we additionally use eye tracking and find that buyers focus more on value decreasing attributes than sellers (and vice versa for value increasing attributes). This shift in attention plays a pivotal role in the construction of value and partially mediates the endowment effect.