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Mary Ann McGarrett is the younger sister of Steve McGarrett, the daughter of John McGarrett and Doris McGarrett and the adoptive mother of Joan McGarrett.


Early life

Mary grew up with her older brother, Steve, and her parents, Detective John McGarrett and teacher/CIA agent Doris McGarrett in Honolulu, Hawaii.

Twenty years ago, Doris allegedly died, leaving their father to raise them alone. Unknown to Mary and Steve, John was investigating the Yakuza that ultimately led to Doris's "death".

Fearing for Mary and Steve's safety, John sent them to the mainland, separated, with both of them not knowing his true intentions.

Doris was presumed to have a huge emotion toll on Mary and her relationship with John and Steve became strained because of it. Sometime after that, she moved to Los Angeles.

Season 1

In Lanakila, on the day she arrived in Hawaii, Mary is arrested for a federal offense, as she signaled a smoke alarm. Her brother, Steve McGarrett, releases her under his custody. As the two officers leave, Mary apologizes for "messing up." Steve however, comments that he didn't see Mary at their father's funeral. Mary then reminds Steve that she hasn't seen him since their mother's funeral, and ponders out loud why they can't have reunions like normal families have. Later on a crime scene, Steve tells Mary to stay in the car. Mary tells him that she is not a dog and promptly starts barking. At Steve's request, Mary is taken to his office for the time being.

A couple of hours later, Steve arrives to change his shirt apologizing to Mary for the wait. Mary is apparently not forgiving, as she asks if his idea of a welcome plan was to pin her to a cop; Steve replies that he's trying to keep her out of prison. Mary then stands up and fixes the collar of his shirt, saying that "you're like seven years old." Mary then confesses that she felt that she was invisible to their father. Steve explains to Mary that their father did love them; he just didn't know how to show it. Steve introduces Mary to Danny Williams who, like Steve, makes fun of Danno's tie, and Kamekona, who is her "babysitter," much to Mary's displeasure. Shortly after Steve and Five-0 return, Kamekona confesses that Mary slipped out while helping him reconcile with an ex-girlfriend. Steve is able to find Mary by their father's graveside, and walks over to her carrying a paper bag. Mary sees him and asks what's in it and Steve smiles, telling her it was lunch. They both sit down and have the family picnic that Mary wanted.

A week later, Mary is living in Steve's house. Early in the morning, Mary bumps into Catherine Rollins, who was staying over with Steve. Mary introduces herself and comments on the "big night" Catherine had last night. Catherine looks confused, and Mary tells her that the house is old and has thin walls. Catherine, realizing what she means, blushes. Mary reassures her that it isn't a problem. "I'm planning to have a lot of guys over, so it'll be a fair fight." Later that night and with Catherine at work, Mary is sitting down watching TV when a commercial advertising the "Hawaii Chair" comes up. Mary tries to change the channel, but is unsuccessful. Mary tries to find batteries, also unsuccessful, and pulls out the "Champ" box. She calls Steve, and asks him why there are pictures of burnt people and postcards from Japan in the toolbox. Steve instructs Mary to put the box back, as it is evidence for a crime. Although Mary tells Steve that she will put the box back, Mary is seen searching in the box and taking pictures.

In Nalowale (episode), the Champ box gets stolen from Steve's house by the Yakuza. Steve soon realizes that the only person that he talked to about the box was Mary, and hurriedly goes to check on her with Danny. They find no sign of Mary in her rental home, but they find blood and a tooth, which, later proves to not be Mary's. Mary calls Steve on her phone. She explains she is in a trunk in a car, and Steve tells her to kick the back taillight and tell him what she sees. With Mary's description, Steve and Danny are able to rescue her. Steve brings something for a bandaged Mary to drink in his office. Mary explains to Steve that she told everyone in HPD about the case of their mother's murder, and also tells him that since the Champ box is stolen, she has another way: her cellphone which she took every picture in the box.

Later that day, Steve takes Mary to the airport to L.A. They share a hug as the airport calls for the passengers to board. Steve promises Mary that they will see each other again.

Season 2

In Kalele, Mary returns (with a much shorter haircut), having acquired a job as a flight attendant. Briefly meeting with Steve and Danny, she returned to her hotel room, where she was held at gunpoint by a diamond smuggler, who made her carry diamonds to deliver to New York, in exchange for her friend, Angela Branson, but after a call from Kaleo, who was Angela's ex-brother-in-law, got to TSA, they detained her before discovering the whole plot was to frame her. The diamonds were then stolen by Angela's ex-husband and Kaleo's brother, Daryl and returned to her, where she would eventually be killed by elderly smuggler August March. At the end of the case, Mary joined he rest of the Five-O team to celebrate Steve's birthday.

Season 3

Mary reappears in Ohuna, now working as a caregiver, and comes to Hawaii with senior citizen Morty, who has always wanted to visit Hawaii.

When Steve tries to arrange the reunion between Mary and Doris, she is very reluctant for it. Doris later sees her at John's grave, crying. Mary is angry at Doris for faking her death.

Later, Mary and Morty are seen on the beach. Morty tells Mary that he himself once had a fight with his daughter, then they didn't speak for years, before Morty received news that his daughter was dead. He convinces Mary to give Doris a second chance, which she does.

Season 4

Mary returns in Ua Nalohia where it's later revealed that she's adopted a baby girl whom she names Joan McGarrett. After Mary falls ill, due to food poisoning, Steve is forced to bring the baby to the office while Mary recovers. During that time, Steve, Chin and Danny take turns in caring for Joan.

After Mary recovers, she returns to the building to get Joan and learns that Steve actually enjoyed his time with the baby.


Although Mary is an adult, her behavior is often similar to a teenager. Steve feels responsible for her, as Mary is often out of control and erratic. Mary also seems to resent her father, and her brother in a similar way, because they see each other. Mary believes that she and Steve meant nothing to their father, and that their father didn't love them. Despite her tough exterior, Mary is shown to deeply love and care for her brother, even though they haven't talked to each other in ten years. Upon her departure, Mary hugged Steve goodbye, signaling that she forgave him for the ten-year gap.


  • It is implied that the creators of Five-0 named her after Mary MacArthur, the older half-sister of James MacArthur, who played Danny in original 1968 Hawaii Five-O. Mary MacArthur was an inspiring stage actress, but died from polio at the age of 19 in 1949.
  • A deleted scene for Pilot revealed Mary was indeed at her father's funeral, but turned up high and flirting with officers. They only used part of that scene when Steve is reflecting on the funeral and the back of Mary's head can be seen.
Season One
Pilot Ohana Malama Ka Aina Lanakila Nalowale Ko'olauloa Ho'apono Mana'o Po'ipu Heihei Palekaiko Hana 'a'a Makehewa
Ke Kinohi He Kane Hewa'ole Kai e'e E Malama Powa Maka Moana Loa Aloha Ne Me'e Laua Na Paio Ma Ke Kahakai Ho'opa'i Ho'ohuli Na'au Ua Hiki Mai Kapalena Pau Oia'i'o
Season Two
Ha'i'ole Ua Lawe Wale Kame'e Mea Makamae Ma'eme'e Ka Hakaka Maika'i Ka Iwi Kapu Lapa'au Ike Maka Kil'ilua Pahele Alaheo Pau'ole
Ka Ho' Oponopono Pu'olo Mai Ka Wa Kahiko I Helu Pu Kupale Lekio Kalele Ha'alele Pa Make Loa Ua Hopu Ua Hala
Season Three
La O Na Makuahine Kanalua Lana I Ka Moana Popilikia Mohai I Ka Wa Mamua Ohuna Wahine'inoloa Ha'awe Make Loa Huaka'I Kula Kahu Kapu
Olelo Ho'Opa'I Make Hana I Wa 'Ia Hookman Kekoa Pa'ani Na Ki'i Hoa Pili Olelo Pa'a Imi Loko Ka 'Uhanet Ho'opio He Welo 'oihana Aloha, Malama Pono
Season Four
Aloha ke kahi I ke kahi A'ale Ma'a Wau Ka 'oia'i'o ma loko A ia la aku Kupu'eu Kupouli 'la Ua Nalohia Akanahe Ha'uoli La Ho'omoaika'i Ho'onani Makuakane Pukana
O kela me keia manawa Hana Lokomaika'i Na Hala a ka makua Pale'la Hoku Welowelo Ma lalo o ka ili Ho'i Hou Ku I Ka Pili Koko Pe'epe'e Kanaka Makani 'Olu a Holo Malie O ka Pili'Ohana ka 'Oit
Season Six
Mai ho`oni i ka wai lana mâlie Lehu a Lehu Ua 'o'oloku ke anu i na mauna Ka Papahana Holo Pono Ka 'alapahi nui Na Pilikua Nui Na Kama Hele Piko Pau 'iole Hana Keaka Ka Makau kaa kaua Kulean Ua Ola Loko I Ke Aloha Umia Ka Hanu
Hoa 'Inea Ke Koa Lokomaika'i Ka Pohaku Kihi Pa'a Waiwai Kanaka Hahai Malama Ka Po'e Ka Haunaele Ka Pono Ku'oko'a I'ike Ke Ao Pilina Koko Pa'a Ka 'Ipuka I Ka 'Upena Nananana O Ke Ali'I Wale No Ka'u Makemake
Season Nine
Cocoon The Man Who Fell from the Sky When the Sea Draws Out the Tidal Wave, the Rocks Where the Cowries Hide Are Exposed On the Slope of the Cliff, Not One Jutting Rock is Hidden from Sight Nothing More the Eyes to Search For Is Borne on the Back; Is Borne in the Arms The Smoke Seen in the Dream Now Rises Birds of a Feather... Truth Comes from the Night When the Light Goes Out, the House Is Dark Gone on the Road from which There Is No Returning A Bruise Inflicted on an Innocent Person Vanishes Quickly Those Above are Descending
Depressed with the Heat of Kealwalua Made Prisoner by the Reign of the Rain When Covetousness is Conceived, Sin is Born Offer Young Yaro Leaves to He Who Eats 'Ape is Bound to Have His Mouth Itch The Octopus of the Deep Spews It's Ink Way of the Gun Offspring of an Owl The Teacher, the Pupil - Let it Come Forth A Stranger Only for a Day The Hand is at Fault Endlessly Pours the Rain of Waianae

Family Tree

Steven McGarrett
Debora McGarrett
John McGarrett
Doris McGarrett
Steve McGarrett
Mary McGarrett
Joan McGarrett