Wh-in-situ constructions in Mandarin Chinese, as opposed to their English counterparts that front wh-phrases to the beginning of the sentence, have the same word order as regular non-wh declaratives. We argue that despite their surface word order, processing wh-in-situ constructions involves constructing a covert non-local syntactic dependency between the in-situ wh-phrase and a higher scope position at a clause boundary, leading to behavioral patterns similar to those associated with the processing of overt dependencies. In two comprehension experiments, we showed that the process of linking an in-situ wh-phrase and its scope position induces a similarity-based memory interference effect if another clause boundary position intervenes. In addition, a set of sentence completion studies also showed that the production of wh-in-situ constructions is heavily modulated by the increased working memory burden that results from planning and maintaining a non-local dependency.