Although many theories of attention assume that attending to an object results in the processing of all its feature dimensions, there has been no direct evidence that the irrelevant dimensions of an attended non-target object are encoded. This article explores factors that modulate such processing. In six experiments, participants made a speeded response to a probe preceded by a prime that varied in two dimensions. Their reaction times to the probe were influenced by the response compatibility between the relevant and irrelevant dimensions of the prime. Furthermore, the effect was observed only when attention was directed to a non-location object feature and when participants’ reaction times were relatively long. These results suggest that the effect of attention on a nontarget object is more complex than was previously understood.