In appearance, they are compact flies without major bristles, but many species have a bee-like hairiness on their bodies, and some are bee or wasp mimics.

The squamae are disproportionately large, completely covering the halteres, and the abdomen has an inflated appearance, often practically globular.

They are members of the infraorder Muscomorpha, and DNA studies suggest that they are most closely related to the families Nemestrinidae and Bombyliidae.

Mature larvae pupate outside the host.The adults of most species, like various members of the Tabanidae, Nemestrinidae, and Bombyliidae, are nectar feeders with exceptionally long probosces, sometimes longer than the entire body length of the insect.

Unlike the other families, however, when not deploying the proboscis for feeding, the Acroceridae carry it lengthwise medially beneath the body, instead of projecting forward.

As a result, the proboscis might escape casual notice, though careful inspection may reveal it projecting slightly behind the abdomen.