Fifty-one Muslims, 47 male, and 4 females were killed in the attacks: 44 at the Al Noor Mosque and 7 at the Linwood Islamic Centre.

One of the victims died shortly after in Christchurch Hospital, while another died in hospital on 2 May, seven weeks after the attack.

Those killed were between 3 and 77 years old. The hospital's Chief of Surgery said on 16 March that four had died in ambulances en route to the hospital.

Forty others were injured: 35 at the Al Noor Mosque and 5 at the Linwood Islamic Centre. On 17 March, Commissioner Bush said 36 were being treated for gunshot wounds in the hospital.

Two were in a serious condition, and a 4-year-old girl was transferred to Starship Hospital in Auckland in a critical condition.

In the days following the attacks, dozens of people remained missing and several diplomatic offices and foreign ministries released statements regarding the number of victims from their nations.

Police requested that people listed as missing, though actually safe, register themselves on the Restoring Family Links website. The New Zealand Red Cross published a list of missing people which included nationals of Afghanistan, Bangladesh, India, Indonesia, Jordan, Malaysia, Pakistan, and Saudi Arabia.

Among the dead listed in New Zealand, Police media releases were citizens of Bangladesh, Egypt, Fiji, India, Indonesia, Iraq, Jordan, Malaysia, Mauritius, New Zealand, Pakistan, and Palestine.

A citizen from Turkey died in the hospital in early May. Atta Elayyan, an IT entrepreneur and goalkeeper for the New Zealand national futsal team, was among those killed.

Brenton Harrison Tarrant, a 28-year-old man from Grafton, New South Wales, Australia, was arrested shortly afterward. He was described in media reports as a white supremacist and part of the alt-right. He had live-streamed the first shooting on Facebook, and prior to the attack, had published an online manifesto; both the video and manifesto were subsequently banned in New Zealand and Australia.

After the police investigation, he was charged with 51 murders, 40 attempted murders, and engaging in a terrorist act. He initially pleaded not guilty to all charges, with the trial expected to start on 2 June 2020.

On 26 March 2020, he changed his plea to guilty on all charges. He was sentenced to life imprisonment without the possibility of parole on 27 August 2020. It was the first time life imprisonment without parole sentence was handed down in New Zealand.