This event-related brain potentials (ERP) study investigated the neurocognitive mechanisms underlying the auditory processing of verbal complexity in French illustrated by the prescriptive present subjunctive mode. Using a violation paradigm, ERPs of 32 French native speakers were continuously recorded while they listened to 200 ecological French sentences selected from the INTEFRA oral corpus (2006). Participants performed an offline acceptability judgement task on each sentence, half of which contained a correct present subjunctive verbal agreement (reçoive) and the other half an incorrect present indicative one (peut). Critically, the present subjunctive mode was triggered either by verbs (Ma mère desire que j’apprenneMy mother wants me to learn) or by subordinating conjunctions (Pour qu’elle reçoiveSo that she receives). We found a delayed anterior negativity (AN) due to the length of the verbal forms and a P600 that were larger for incongruent than for congruent verbal agreement in the same time window. While the two effects were left lateralized for subordinating conjunctions, they were right lateralized for both structures with a larger effect for subordinating conjunctions than for verbs. Moreover, our data revealed that the AN/P600 pattern was larger in late position than in early ones. Taken together, these results suggest that morphosyntactic complexity conveyed by the French subjunctive involves at least two neurocognitive processes thought to support an initial morphosyntactic analysis (AN) and a syntactic revision and repair (posterior P600). These two processes may be modulated as a function of both the element (i.e., subordinating conjunction vs verb) that triggers the subjunctive mode and the moment at which this element is used while sentence processing.