Actor Samuel West, who plays vet Siegfried Farnon, shared a photo of himself with co-star Callum Woodhouse, who plays his brother Tristan, on the set this week.
Although the shoot's exact location has not been confirmed, the cast and crew are likely to return to previous haunts in the southern Dales.
Grassington is used for the fictional town of Darrowby, and interior scenes set at The Drover's Arms pub are filmed at The Green Dragon in Hardraw and exteriors at The Devonshire Arms in Grassington. Some scenes are also shot in Arncliffe.
Dales farms and churches have also appeared in the previous two series and Christmas specials, while Mrs Pumphrey's home is Broughton Hall near Skipton. Studley Royal deer park, Birstwith Hall and Ripley Castle, all in the Harrogate and Ripon area, featured in series two.
When producers needed a more urban backdrop to look convincing as James Herriot's home city of Glasgow, they took the shoot to Little Germany in Bradford, a district of neoclassical Victorian warehouses built by German Jewish merchants that is often used for filming. Netflix recently took over the area to shoot series five of The Crown, with the streets standing in for 1990s Moscow.