One hundred and twenty-one MPs were elected to the New Zealand House of Representatives, 70 from single-member electorates, and 51 from party lists including one overhang seat.

Following the election, National reentered into confidence and supply agreements with ACT and United Future on 5 December 2011,[6][7] and with the Māori Party on 11 December 2011,[8] to form a minority government with a seven-seat majority (64 seats to 57) and give the Fifth National Government a second term in office.

[9] Breaking with tradition, Prime Minister John Key announced the election date in February.

Traditionally, the election date is a closely guarded secret, announced as late as possible.

[10] Under section 17 of the Constitution Act 1986, Parliament expires three years "from the day fixed for the return of the writs issued for the last preceding general election of members of the House of Representatives, and no longer."

[13] The Christmas/New Year holiday period made the last realistic date for the election Saturday 10 December 2011.

The Rugby World Cup 2011 was hosted by New Zealand between 9 September and 23 October 2011, and ruled out all the possible election dates in this period.

Carter continued as an independent, while Harawira resigned from parliament to recontest his Te Tai Tokerau electorate in a by-election under his newly formed Mana Party.

One of the ACT MPs, John Boscawen, contested Tāmaki, but did not expect to win and was not on the party list.

On 17 September 2010, Justice Minister Simon Power announced the government was introducing legislation making this the first election where voters would be able to re-enrol completely on-line.

[36] Voters in the Christchurch region were encouraged to cast their votes before election day if they had doubt about being able to get to a polling booth on election day or to avoid long queues, as many traditional polling booths are unavailable due to the earthquakes.

Seventeen independent candidates also contested the electorates in thirteen electorates: Christchurch Central, Coromandel, Epsom (two), Hamilton West (two), New Plymouth, Ōtaki, Rangitikei (two), Rongotai, Tāmaki (two), Tauranga, Waitaki, Wellington Central, and Ikaroa-Rawhiti On 11 November, National Party leader John Key met with John Banks, the ACT candidate for Epsom, over a cup of tea at a cafe in Newmarket to send a signal to Epsom voters about voting tactically.

This would allow ACT to bypass the 5% party vote threshold and enter Parliament by winning an electorate seat, thereby providing a coalition partner for National.

In the month leading up to the election, the big four newspapers in New Zealand – The New Zealand Herald, The Herald on Sunday, The Dominion Post and The Sunday Star-Times – printed 72 percent more photos of Key than his opponent, Phil Goff, and devoted twice as many column inches of text coverage.

[54] The nature of the Mixed Member Proportional voting system, whereby the share of seats in Parliament a party gets is determined by its share of the nationwide party vote, means aside from normal polling bias and error, opinion polling in New Zealand is fairly accurate in predicting the outcome of an election compared with other countries.

[56] A National or Labour candidate took second place in all the general electorates except Rodney, where it was Conservative Party leader Colin Craig.

Christchurch Central on election night ended with incumbent Labour MP Brendon Burns and National's Nicky Wagner tied on 10,493 votes each, and on official counts, swung to Nicky Wagner with a 45-vote majority, increasing to 47 votes on a judicial recount.

[58][59] Despite losing their electorate seats, Chris Auchinvole and Clayton Cosgrove were re-elected into parliament via the party list.

On election night, Waitakere was won by incumbent National MP Paula Bennett with a 349-vote majority over Labour's Carmel Sepuloni.

New MPs: Scott Simpson, Maggie Barry, Mike Sabin, Ian McKelvie, Mark Mitchell, Simon O'Connor, Alfred Ngaro, Jian Yang, Paul Goldsmith, David Clark, Rino Tirikatene, Megan Woods, Andrew Little, Eugenie Sage, Jan Logie, Steffan Browning, Denise Roche, Holly Walker, Julie Anne Genter, Tracey Martin, Andrew Williams, Richard Prosser, Denis O'Rourke, Asenati Taylor, Brendan Horan Returning MPs: John Banks, Winston Peters, Barbara Stewart Defeated MPs: Paul Quinn, Steve Chadwick, Stuart Nash, Carmel Sepuloni, Rick Barker, Rahui Katene Defeated MPs who later returned during the 50th Parliament Aaron Gilmore, Carol Beaumont, Kelvin Davis The Electoral Commission released party electoral expense returns on 21 March 2012, stating how much each party spent on campaigning between 26 August and 25 November 2011.