School systems across the country are transitioning from paper-based testing (PBT) to computer-based testing (CBT). As this technological shift occurs, more research is necessary to understand the practical and performance implications of administering CBTs. Currently, there is a paucity of research using CBTs to examine working memory (WM) performance, even though CBTs may negatively influence performance. The present study compared a WM CBT and PBT and found enhanced WM performance on the PBT across several verbal and visuospatial WM tests. This pattern was evident even after age was controlled, indicating that test mode effects were persistent across ages (4-11 years). CBTs on WM performance may yield lower scores due to developmental WM differences, increased cognitive workload, test mode effects stemming from individual access to technology, and participant characteristics, such as developmental, biological, or gender differences. The presence of divergent WM in CBT and PBT indicates the need for additional options for children at risk of academic failure because of testing modality.