Fans got the happy ending they had been waiting for as the title character, created by Miranda Hart, got married.
The New Year's Day episode had 7.3m viewers, according to overnight figures.
The first part of the finale, shown on Christmas Day, had 6.7m viewers overnight.
Writing in The Independent, Neela Debnath said Miranda had drawn to a close "with a sweet and heart-warming ending".
"It's surprisingly touching and quite tender - that's not to say there aren't any pratfalls - but the finale is about Miranda standing up to her mother and accepting herself as she is."
Gerard O'Donovan, writing for The Telegraph, said: "New Year's Day brought all the humour and joy we could have wanted in a masterclass of romantic comedy writing and performance that teased and toyed, then delivered big on the happy ending, with a wedding."
Mark Lawson, writing in The Guardian, said: "As admirers had hoped, Miranda ended up on the floor twice in her comedy send-offs.
"But her expanding career, of which her inventive and well-acted sitcom is only a small part, suggests that her detractors are unlikely to get their wish of her falling metaphorically flat on her face."
Before the final show aired, Hart tweeted: "Happy New Year Day and goodbye to my creative baby day. 8pm BBC One. Can't promise but you MIGHT get a glimpse of that @GaryBarlow."
The show, which was first shown on BBC Two in 2009 before moving to BBC One, follows the trials and tribulations of Hart's character, a shop owner prone to committing social faux pas.
The programme also sees Patricia Hodge as her TV alter-ego's mother and Sarah Hadland as her shop's assistant manager.
The show, and its star, has won accolades from the Royal Television Society and the British Comedy Awards, among others.
The first episode of the third series was the most-watched television programme at Christmas in 2012.
The 41-year-old actress and comedienne is to star alongside Jude Law and Melissa McCarthy in American comedy Spy.
The film, directed by Bridesmaids' Paul Feig, is due to be released in UK cinemas in May.
An autobiographical book about Hart's life with her dog Peggy, Peggy And Me, will be also released this year.

Noss Primary in Wick is closed until 30 May following what Highland Council described as a "significant failure" at the Â£15.4m building on Tuesday.
Gail Ross, who is the local MSP and a councillor, said it was "a saving grace" that pupils were having their lunch and not in the rooms at the time.
The new school only opened to pupils last month.
It was built as a replacement for Wick's North and Hillhead primary schools.
Ms Ross, who helped to unveil the name for the new school in 2014, described Tuesday's burst as "worrying" and "concerning".
She told BBC Radio Scotland: "I spoke to the headmaster yesterday. He told me he came upon it in the corridor and its was like a sauna - a boiling hot water pipe had burst above two classrooms.
"The only saving grace was that the children were in the dining hall at the time because it doesn't bear thinking about the consequences of that if the kids had been in the classrooms."
Highland Council said the school was closed "due to a significant failure" of a hot water connection to the heating system in the ceiling of the east wing of the building.
The local authority said work repairing and testing the system was expected to take three days.
Graham Nichols, an officer at Highland Council, said: "While this is disappointing, the testing will give us confidence in the integrity of the water systems, and allow additional time for the building to dry out."
TV critics are full of praise for the finale of sitcom Miranda, which has bowed out after five years.
[NEXT_CONCEPT]
A "boiling hot" water pipe burst above two classrooms at a new school, an MSP has revealed.