The phenomenon of verb complementation has been a challenging research topic in the domain of first and second language acquisition in recent decades. This study aimed to determine the achievement levels of learners of English as a foreign language (EFL) in terms of their recognition and production of factive cognitive verb complementation patterns and their associated senses. Specifically, the factive verbs analyzed within the scope of the study were: "know, understand, regret, remember," and "forget," along with their complementation patterns and senses. Data were collected from 269 Turkish EFL learners through four types of tests developed by Atasever Belli (2019). Learners' receptive knowledge was measured through "the Grammaticality Judgment Test" and "Fill-in-the-Blank Test." Their productive knowledge was assessed through the "Free-Production Test" and "Sentence Completion Test." Data obtained from the participants' responses to tests were analyzed both quantitatively and qualitatively. This study demonstrated that word knowledge level has a significant impact on verb complementation performance both at receptive and productive levels. It also revealed that production test performance exceeded recognition test performance. The performance differences were analyzed by considering factors such as linguistic transfer, vocabulary knowledge, test types, verb properties, context, and input exposure. These results highlight learners' interlanguage development and offer profound pedagogical implications. [Note: The page range (7-36) shown in the citation is incorrect. The correct page range is 7-35.]