<p>Cognitive effects of cellphone dependency among young adults have garnered increasing research attention. While cellphones have been identified as a distractor in daily tasks, related psychological processes remain unclear. As a potential mechanism underlying those effects of cellphones, excessive working memory (WM) load has not yet been well examined. Our study investigated the effects of the mental representation of cellphone separation on WM. Seventy-five participants (<i>M</i>_<i>age</i> = 21.3&#xa0;years; 55 females, 20 males) were assigned into three groups: the cued separation, natural separation, or control group, and completed a block of choice reaction time (CRT) task, and a dual-task block: the CRT and a concurrent WM task. CRT performance was analyzed using the ex-Gaussian model, providing the parameters <i>μ</i> and <i>τ</i> to reflect lower-order processing and top-down control, respectively. Results showed that WM load reduced cognitive performance, with the cued separation group exhibiting the largest performance impairments, and ex-Gaussian <i>μ</i> and <i>τ</i> were sensitive to WM load and cellphone separation. Our findings suggest that the mental representation of cellphone separation, especially when cued, depletes cognitive resources, and impairs executive functions, which highlight the need for strategies to mitigate the cognitive costs of cellphone dependency, particularly in high-stakes applied contexts.</p>