The copious corpus of deviations from standard Latin from Trier spans more than 800 years (50 BC–800 AD) and comprises both pagan and Christian inscriptions, the latter exclusively on tombstones. This paper points out the most salient non-standard features in the categories of phonetics, morphology, syntax and vocabulary. Most of them conform to standard Vulgar Latin, but some yield features of the inscriptions’ area, such as Western Romance (preservation of final -s, voicing intervocalic stops), Gallo-Romance (qui instead of quae, nasalisation), and the extinct Moselle Romance. A few features might reflect Gaulish substrate influence ([u] > [y], e before nasals > i, ē > ī, ō > ū, -m > -n). Clues for palatalisation and the raisings ē > ī, ō > ū are the most prominent phonetic features, the latter supporting, combined with the preservation of final -s, a renewed paradigm of nominal inflection. Morphosyntactic changes are driven by analogy and regularisations. Starting at the fringes, the erosion of case syntax ended up in a complete breakdown. Christianity fostered the recording of previously undocumented substandard features, completed the assimilation of Celtic (which pagan polytheism and the upwards mobility of Roman society had initiated) and supported the cultural integration of Germanic immigrants.