The Byers Group, exposed on Byers Peninsula, Livingston Island and Snow Island, Antarctica, is a mudstone-dominated sequence deposited in a fore-arc setting. Palynological studies on parts of the Byers Group have provided new data on Early Cretaceous biostratigraphy, palaeoenvironments and palaeoclimate. Dinoflagellate cyst assemblages date the President Beaches Formation as latest Early Berriasian-Berriasian, and a latest Berriasian-earliest Valanginian to Middle Valanginian age is suggested for the Chester Cone Formation. The boundary between the President Beaches and Chester Cone formations is dated as latest Berriasian. Dinoflagellate cyst assemblages permit correlation of the marine mudstones from Snow Island (President Head) within the Byers Group stratigraphy of Byers Peninsula. A marginal, shallow-marine palaeoenvironment is indicated by the palynological content of the Byers Group. Occasionally, there is evidence of slightly deeper marine influence within the President Beaches Formation. The Chester Cone Formation records increased terrestrial influence and possibly exhibits a non-marine signature towards the top of the sequence. Parts of the Chester Cone Formation are affected by reworking. A temperate palaeoclimate with occasional high humidity is suggested for the Byers Group. The land vegetation probably consisted of a coniferous forest with abundant podocarps and araucarians, a fern understorey and minor amounts of lycopods and bryophytes. The Byers Group palynoflora shows strongest affiliation to those from the Mesozoic of Australia and southern South America, although marked provincialism is evident within the Valanginian marine microplankton content.