Purpose: This study investigates the acquisition of aspect markers by Mandarin-speaking children with developmental language disorder (DLD) in comparison to typically developing aged-matched (TDA) children and typically developing younger (TDY) children through the aspect hypothesis (AH). Method: A sentence-picture matching task and a priming picture description task were used to examine and compare the comprehension and production of aspect markers by Mandarin-speaking children with DLD and typically developing children. Participants consisted of 13 children in each of the DLD, TDA, and TDY groups. Results: A similar pattern was found for DLD and TDY groups. However, compared to the TDA group, children with DLD demonstrated lower accuracy and slower reaction times regarding aspect markers "-guo, -le," and "zai-." Children with DLD also produced fewer target aspect markers "-le, zai-," and "-zhe." The overall production of "zai-" and "-zhe" was less than both TDA and TDY groups, and children with DLD omitted the use of aspect markers more often. The influence of lexical aspect was found in the TDA children's understanding of the perfective aspect marker "-le," which is consistent with the predictions of the AH. Conclusion: Results indicate that children with DLD had problems with the acquisition of aspect markers but that their language development was delayed rather than deviant.