The current research explores how awareness of shared attention influences attitude formation. We theorized that sharing the experience of an object with fellow group members would increase elaborative processing, which in turn would intensify the effects of participant mood on attitude formation. Four experiments found that observing the same object as similar others produced more positive ratings among those in a positive mood, but more negative ratings among those in a negative mood. Participant mood had a stronger influence on evaluations when an object had purportedly been viewed by similar others than when (a) that same object was being viewed by dissimilar others, (b) similar others were viewing a different object, (c) different others were viewing a different object, or (d) the object was viewed alone with no others present. Study 4 demonstrated that these effects were driven by heightened cognitive elaboration of the attended object in the shared attention condition. These findings support the theoretical conjecture that an object attended with one's ingroup is subject to broader encoding in relation to existing knowledge structures.