The forward testing effect (FTE) is a phenomenon where testing previously learned information enhances memory for subsequently acquired new information. Recent research has indicated that the FTE may persist when the previously learned and the new information are semantically related but might diminish after a 25-minute retention interval for unrelated material. In this study, we re-examined the impact of retention interval on the FTE using unrelated word lists. A total of 128 participants studied three lists of unrelated words in anticipation of a final cumulative recall test. Participants were tested immediately on lists 1 and 2 (testing condition) or restudied lists 1 and 2 after initial study (restudy condition). Following the study of the critical third list, a retention interval of either 1 minute or 25 minutes was imposed before recall testing for this list. The results of the list 3 criterion test demonstrated a significant main effect of retention interval, with lower recall rates after the longer (25-minute) interval compared to the shorter (1-minute) interval. More importantly, the FTE was consistently observed in both the short and long retention interval conditions, which contrasts with the previous research findings. We conducted further analysis of the role of the retention interval through a meta-analysis of FTE studies and discuss our results in the context of current FTE theories.