This paper is a descriptive investigation of past participle agreement in Old Romanian. It is shown that the passive past participle constantly agreed with the subject; in contrast, the past participle serving as a tense/mood formative showed agreement variations, unlike in Modern Romanian, where it is invariable. Variation occurs when the auxiliary is ‘be’, with transitive verbs (when there is no possible confusion with the passive construction), and with unaccusative verbs (which do not allow passivization and consequently agreement cannot led to confusions). The agreement of the formative past participle has been lost in standard Modern Romanian but it is still attested in certain regional varieties, either with the auxiliary ‘be’ or with the auxiliary ‘have’. Special constructions (i.e. past participle agreement with the direct object, the past participle with the ending -ă, the ‘fake’ agreement of the past participle) are also taken into consideration. The paper underlines, on the one hand, the differences between Old Romanian and Modern Romanian and, on the other hand, the differences and similarities between (Old and Modern) Romanian and other Romance languages.