Serial order is an essential but still poorly understood component of verbal working memory (WM). This study examined the role of spatial vs. temporal codes for the representation of serial order information by presenting spatial or temporal secondary tasks during the completion of a verbal WM task. The secondary tasks were dot detection tasks designed to impact spatial processing (the dots appeared in random vs. left-to-right spatial order) or temporal processing (the dots appeared in regular vs. irregular temporal order). In two experiments, we observed an exclusive, interfering impact of the temporal secondary task on serial order WM while evidence for the null was observed for the impact of the spatial secondary task. These data provide support for an intervention of temporal processes in the encoding of serial order information in WM. Furthermore, the effect of temporal interference was not limited to WM for serial order information, but also disrupted WM for item information. These findings highlight the role of temporal processes in encoding both item and serial order information in WM, possibly by allowing binding of the two types of information.