In certain English finite complement clauses, inclusion of the complementizer that is optional. Previous research has identified various factors that influence when native speakers tend to produce or omit the complementizer, including syntactic weight, clause juncture constraints, and predicate frequency. The present study addresses the question to what extent German and Spanish learners of English as a second language (L2) produce and omit the complementizer under similar conditions. 3,622 instances of English adjectival, object, and subject complement constructions were retrieved from the International Corpus of English and the German and Spanish components of the International Corpus of Learner English. A logistic regression model suggests that L2 learners’ and natives’ production is largely governed by the same factors. However, in comparison with native speakers, L2 learners display a lower rate of complementizer omission. They are more impacted by processing-related factors such as complexity and clause juncture, and less sensitive to verb-construction cue validity.