Downton Abbey creator would like to introduce black or Asian characters into the period drama set in an English country home.
Writer Julian Fellowes said it would "be rather nice to open it up ethnically a bit".
Speaking to the Daily Telegraph, he said: "Oh I think that’s rather a good idea. You have to work it in in a way that is historically believable, but I am sure we could do that."
"[The show] certainly ought to have an Indian character from that period.”
The current cast of genteel aristocracy and hardworking servants is entirely Caucasian.
Fellowes' remarks come after last night's conclusion to the third series of Downton broke ratings records with 10.7 million viewers tuning in to watch an extended instalment.
The episode was the highest-rated of the series which saw US star Shirley MacLaine join the likes of Dame Maggie Smith and Hugh Bonneville.
Downton Abbey averaged 9.7 million viewers across the series, making it the highest-rating drama of the year so far, ITV said.
BBC1 hit Call The Midwife averaged 8.7 million viewers, while Sherlock had 8.3 million.
The 9.7 million average is also the highest for a series of Downton, created by Julian Fellowes, to date.
Last night's finale attracted a peak of 10.7 million viewers and an average of 10.1 million, including viewers watching on the +1 catch-up channel.
Based on average rather than peak viewing figures, Downton Abbey was the most-watched programme on TV last night.
The second series of Downton Abbey concluded on ITV1 with an average of 10.7 million viewers.
No official announcement has been made about a fourth series of Downton, in which a new character appeared last night.
A special festive episode will be broadcast this Christmas.