Prospective memory defines the ability to remember and carry out intended actions in the future. Working memory is used to temporarily hold and manipulate information. There is indirect evidence that prospective memory and working memory share cognitive processes. However, direct evidence for this assumption is largely missing. Hence, it was our primary goal to provide more direct evidence by means of a dual task approach that prospective memory and working memory share cognitive processes. Working memory was tested with a delayed estimation task. The task required participants to memorize colored objects, which color had to be reproduced during recall. After measuring baseline performance with the delayed estimation task, participants received the prospective memory instructions to disregard the displayed color of an object if it belonged to a specific category, such as animals, and to reproduce a particular shown color, such as a specific tone of red. After a retention interval with an unrelated filler activity, participants were required to again conduct the delayed estimation task, this time with the embedded prospective memory cues. Participants completed three conditions with increasing working memory loads, each consisting of a baseline and a prospective memory block. Preliminary results showed reduced precision in color recall in prospective memory blocks in comparison to baseline blocks. The difference in color recall between prospective memory block and baseline block increased with increasing working memory loads. In line with previous research, we conclude that working memory and prospective memory share common cognitive processes.