The present invention relates to novel liquid pharmaceutical compositions of adalimumab, which include adalimumab or a biosimilar thereof, an acetate buffering agent/system such as sodium acetate/acetic acid, and a sugar stabiliser such as trehalose. Such a combination of components furnishes formulations having a stability (e.g. on storage and when exposed to stress) which is comparable to or an improvement upon those known in the art, and with fewer ingredients. Such advances will help adalimumab treatments to become more widely available at lower cost, and prolong the viability of pre-loaded delivery devices (e.g. pre-filled syringes) to reduce unnecessary waste of the drug.