Series Three was broadcast in January 2016. On 2 February 2015, it was announced that the show had been renewed for a third series.
In April 2015, the third series began filming. On the 13th of May, actors Rupert Everett and Matthew McNulty were announced in the roles of Philippe Achille and Lucien Grimaud, respectively. On May the 19th, it was revealed that Milady de Winter would not appear in the early episodes of Series Three due to the actress' pregnancy.
Mid-season it was reported BBC was not picking the show up for a new series, and this would be the last.
Athos, D'Artagnan and Porthos have spent the past five years on the war front fighting the Spanish. Aramis has been at a monastery helping to care for orphaned children. Through the course of battle, The Musketeers fall together again and return to Paris. The Maquis de Feron has been given Rochefort's position and has control over Captain Marcheaux and his Red Guard. King Louis XIII is still dying but not even Queen Anne is aware.
- Athos - Tom Burke (10 episodes)
- Aramis - Santiago Cabrera (10 episodes)
- Porthos - Howard Charles (10 episodes)
- D'Artagnan - Luke Pasqualino (10 episodes)
- Queen Anne - Alexandra Dowling (10 episodes)
- Lucien Grimaud - Matthew McNulty (10 episodes)
- Constance - Tamla Kari (9 episodes)
- Captain Treville - Hugo Speer (9 episodes)
- King Louis XIII - Ryan Gage (9 episodes)
- Captain Marcheaux - Matt Stokoe (9 episodes)
- Sylvie - Thalissa Teixeira (9 episodes)
- Maquis de Feron - Rupert Everett (6 episodes)
- The Dauphin - Robby Fisher (6 episodes)
- Cadet Brujon - Tom Morley (6 episodes)
- Gaston - Andre Flynn (5 episodes)
- Milady de Winter - Maimie McCoy (2 episodes)
- Elodie - Lily Loveless (2 episodes)
- Duke of Lorraine - Robert Glenister (2 episodes)
|1||"Spoils of War"||Simon J. Ashford||Andy Hay||2016|
|2||"The Hunger"||Simon J. Ashford||Andy Hay||2016|
|3||"Brothers in Arms"||Simon Allen||Roger Golby||2016|
|4||"The Queen's Diamonds"||Jeff Povey||Nicholas Renton||2016|
|5||"To Play the King"||Ellen Taylor||-||2016|
|6||"Death of a Hero"||Peter McKenna||Nicholas Renton||2016|
|7||"Fool's Gold"||Kelly Jones||Susan Tully||2016|
|8||"Prisoners of War"||James Payne||Udayan Prasad||2016|
|9||"The Prize"||Dusty Hughes||Susan Tully||2016|
|10||"We Are the Garrison"||Simon Allen||Udayan Prasad||2016|