This inquiry explored how adult heritage and monolingual speakers of Turkish process evidentiality (the linguistic expression of information source) via finite verb inflections and time reference, voiced on non-finite participles. A sentence-verification task was employed to measure participants’ sensitivity to evidentiality and time-reference violations in Turkish. The findings displayed that the heritage speakers were less precise and slower than the monolinguals in replying to both evidentiality and time-reference violations. Also, the heritage speakers made more errors and had longer RTs when replying to evidentiality violations as compared to time-reference violations. The monolinguals had longer RTs (and more precise replies) to time reference than to evidentiality violations. This inquiry displays that evidentiality is susceptible to incomplete acquisition in Turkish heritage speakers. It is proposed that the claim for simultaneous processing at diverse linguistic levels makes the evidentiality markers vulnerable.