The processability account anticipates that learners will make more underpassivization errors than overpassivization errors since passivization entails more processing. Although one study on psych-verbs and a few on unaccusatives examined Turkish L2 learners’ acquisition, no research compared a single set of learners’ acquisitions of these verbs together from a processing point of view. In this regard, the current study aims to investigate whether the processing complexity of passivization influences acquisition of psych and unaccusative verbs. It also questions whether general accuracy levels in Grammaticality Judgement Task (GJT) and degree of familiarity with target verbs are related to their level of accuracy with individual psych and unaccusative verbs. 33 undergraduate-level university students performed on the GJT and a Word Familiarity Rating Task (WFRT). The GJT included 38 items with 12 sentences for psych-verbs, 12 sentences for unaccusative-verbs, 12 sentences for distracters and 2 sentences for examples. The WFRT was a survey questioning familiarity with 6 psych and 6 unaccusative verbs. To analyse the data, a set of nonparametric tests and descriptive statistics were used. The results revealed that learners performed mor The processability account anticipates that learners will make more underpassivization errors than overpassivization errors since passivization entails more processing. Although one study on psych-verbs and a few on unaccusatives examined Turkish L2 learners’ acquisition, no research compared a single set of learners’ acquisitions of these verbs together from a processing point of view. In this regard, the current study aims to investigate whether the processing complexity of passivization influences acquisition of psych and unaccusative verbs. It also questions whether general accuracy levels in Grammaticality Judgement Task (GJT) and degree of familiarity with target verbs are related to their level of accuracy with individual psych and unaccusative verbs. 33 undergraduate-level university students performed on the GJT and a Word Familiarity Rating Task (WFRT). The GJT included 38 items with 12 sentences for psych-verbs, 12 sentences for unaccusative-verbs, 12 sentences for distracters and 2 sentences for examples. The WFRT was a survey questioning familiarity with 6 psych and 6 unaccusative verbs. To analyse the data, a set of nonparametric tests and descriptive statistics were used. The results revealed that learners performed more accurately on unaccusatives than on psych-verbs. They did more underpassivization errors by accepting ungrammatical active constructions of psych verbs. Their performances on psych and unaccusative verbs went parallel with their general accuracy levels in GJT while their degree of familiarity with and accuracy level for two verbs do not correlate with each other.The results suggest that such factors as processability and L1 transfer seem to impact the acquisition. Keywords:Second language acquisition; psych verbs; unaccusative verbs; underpassivization; overpassivization. e accurately on unaccusatives than on psych-verbs. They did more underpassivization errors by accepting ungrammatical active constructions of psych verbs. Their performances on psych and unaccusative verbs went parallel with their general accuracy levels in GJT while their degree of familiarity with and accuracy level for two verbs do not correlate with each other.The results suggest that such factors as processability and L1 transfer seem to impact the acquisition. Keywords:Second language acquisition; psych verbs; unaccusative verbs; underpassivization; overpassivization.