(Arranged alphabetically by last name)
Warning: There may be spoilers for episodes in the following summariesAdmiral Thomas Boone (played by Terry O'Quinn): A Naval Aviator who was Harm's father's wingmate, Admiral Boone was a strict but good commander. After being accused of war crimes, he decided to retire, despite his claim that he wasn't guilty.
(Episodes Boone has appeared in)
Mic Brumby (played by Trevor Goddard): A former Lieutenant Commander of the Royal Australian Navy, Mic Brumby is in love with Mac. He met her while on an exchange program and, after giving up his military career to be near her, became engaged to her. However, wedding bliss was not to be. Broken hearted, he returned to Australia and the military.
Meredith Cavanaugh (played by Isabella Hofmann): A literature teacher and Shakespeare lover, Meredith met Admiral Chegwidden and seemed to fall in love. She seemed quite bumbling at the start, poor at nearly everything she did, but gradually she improved. Chegwidden proposed to her recently, and she accepted, but something has split them apart recently...
(Episodes Meredith has appeared in)
Petty Officer, First Class, Jennifer Coates (played by Zoe McLellan): Met by the JAG team when she had to stay with Harm over Christmas--after impersonating a bell-ringing Santa and pocketing the money--when all the brigs were closed. Later, she was Bud's partner when he was assigned to the Seahawk. Currently, she works as Admiral Chegwidden's personal yeoman.
(Episodes Coates has appeared in)
Lieutenant Commander Teresa Coulter (played by Trisha Yearwood): A forsenic pathologiest (she examines DNA, fingerprints, and other evidence to determine who did what where), Coulter comes in handy quite a few times. Stationed everywhere from America to Afghanistan, she is good at her job and can do it quickly.
(Episodes Coulter has appeared in)
Lieutenant Colonel John Farrow (played by Ben Murphy): Mac's Commanding Officer when Mac served in Okinawa, Japan. He is currently very close friend of Mac's, although some people suspect that they had, at one point, more than just a friendly relationship.
(Episodes Farrow has appeared in)
Gunnery Sergeant Victor Galindez (played by Randy Vasquez): Galindez transferred to JAG Headquarters as an Administrative Assistant after Harriet left active-duty due to her pregnancy. However, after the war against terrorism began, he requested a transfer to a combat zone. Recently, he's been seen in the company of Clayton Webb.
(Episodes Galindez has appeared in)
Lieutenant Elizabeth "Skates" Hawkes (played by Sibel Ergener): One of the best RIOs in the Navy, Skates is assigned to the USS Seahawk. She was Rabb's RIO when he temporarily returned to flying and was later accused of dereliction of duty, and Harm put everything he had into defending her.
(Episodes Skates has appeared in)
Lieutenant Commander Jack Keeter (played by Michael McGrady): Harm's roommate during Naval Aviation training, Keeter thinks quickly on his feet. He and Harm are good friends.
(Episodes Keeter has appeared in)
Commander Allison Krennick (played by Andrea Thompson): Nicknamed the "Dragon Lady", Krennick was Admiral Chegwidden's aide at one point, making her Harm and Meg's commanding officer when the two were partners. Although tough and ready to bite your head off, Krennick truely does care for her people.
(Episodes Krennick has appeared in)
Congresswoman Bobbi Latham (played by Anne-Marie Johnson): Latham has been both a friend and an enemy to the JAG corps and the military. Although she approves of many of the causes the military and JAG defend, she is reluctant to allow any lives to be risked in their defense. Occasionally, Harm is able to convince her to help him with a case. Also, she and Sturgis were an item at one point, but their romance seems to be over.
(Episodes Latham has appeared in)
Commander Theodore "Teddy" Lindsey (played by W.K. Stratton): At one point, Lindsey was one of the senior lawyers at JAG Headquarters and one of Harm and Meg's superior officers. A weak man, Lindsey has trouble making decisions on the fly and is an extremely by-the-book officer. However, growing bitter about his lack of success, he recently made a serious mistake.
(Episodes Lindsey has appeared in)
Dalton Lowne (played by Larry Poindexter): A civilian lawyer, Lowne was a boyfriend of Mac's until he betrayed her confidence. At one point, he was even able to convince her to resign from the Marines and join his law corporation, although he couldn't keep her there.
(Episodes Lowne has appeared in)
Chloe Madison (played by Mae Whitman): Chloe Madison is Mac's "Little Sister" through the "Big Brother/Big Sister" program. However, she's recently moved away to her grandparent's farm, restricting her conversations with Mac to phone exchanges.
(Episodes Chloe has appeared in)
Lieutenant Commander Tracy Manetti (played by Tamlyn Tomita): Manetti transferred to JAG HQ after being recommended by the new SecNav, Sheffield, but was transferred out again after evaluating the performance of the JAG team. She comes from a line of tobacco farmers in Virginia and has three brothers, all lawyers. She, herself, graduated from Yale Law School, and her father is one of Sheffield's biggest supporters. Manetti has now departed from JAG HQ.
(Episodes Manetti has appeared in)
Former SecNav Nelson (played by Paul Collins): Recently the Secretary of the Navy, Nelson is a tough and sometimes unfair man. Occassionally, he played favorites and he definitely disliked Harm and Mac. He was removed from office after being investigated for not communicating with the intelligence agencies and instead sending Naval officers to do the intelligence work.
(Episodes Nelson has appeared in)
Francesca Paretti (played by Giuliana Santini): Admiral Chegwidden's daughter, Francesca is a fashion editor and lives in Naples, Italy.
(Episodes Francesca has appeared in)
Lieutenant Commander Jordan Parker (played by Susan Haskell): A very serious love interest of Harm's until he dumped her to return to flying. When he returned, she had left for Spain and they never reconciled. Harm moved on to Renee and Jordan apparently suicided soon afterward.
(Episodes Jordan has appeared in)
Renee Peterson (played by Cindy Ambuehl): Nicknamed the "video princess" by Mac, Renee was in charge of recruitment videos when she met Harm. When a mutual attachment grew, they began to date. However, it eventually was broken off.
(Episodes Renee has appeared in)
Commander Caitlin "Kate" Pike (played by Andrea Parker): After graduating from Harvard Law School, Kate was Harm's partner for a little while when she was a lieutenant before she was replaced by Lieutenant (J.G.) Meg Austin. Also, she reappeared a few years later for a short while, both requesting Harm's help and hoping to become his partner again, but decided Mac was much better suited to the job.
(Episodes Kate has appeared in)
Anne Pendry (played by Dahpne Ashbrook): The wife of Harm's deceased friend, Luke Pendry, Anne became romatically interested in Harm, but Harm ruined it. She and her son, Josh, haven't kept in close touch with him.
(Episodes Annie has appeared in)
Lieutenant Harmon Rabb, Senior: Harm's father, Rabb was a Naval Aviator in Vietnam called the Hammer. Shot down during combat, he was given the designation MIA and was presumed dead after a while, although information appeared suggesting that he was alive, especially after Harm discovered a son named Sergei.
Midshipman Mike "Mikey" Roberts (played by Michael Bellisario): Bud's brother, Mikey wanted to be a cartoonist, but eventually decided to join the Navy. After being a Petty Officer for a little while, he was recommended for Officer Training and is currently attending the Naval Academy.
(Episodes Mikey has appeared in)
Bud "Big Bud" Roberts, Senior (played by Jeff MacKay): Big Bud is the abusive father of Bud and Mikey. A heavy drinker and a Master Chief, Big Bud cheated the Navy and made his son Bud be his defendant at his trial. However, he seems to be trying to make up his past actions towards his sons.
(Episodes Big Bud has appeared in)
SecNav Sheffield (played by Dean Stockwell): The most recent SecNav, Sheffield was sworn in after the previous SecNav, Nelson, was thrown out of office. He plays favorites but is a politically savvy man and reasonably fair to his people.
(Episodes Sheffield has appeared in)
Lieutenant Loren Singer (played by Nanci Chambers): One of the least-liked people at JAG Headquarters, Singer, a technically excellent lawyer, often goes too far beyond the call of duty to try to make herself look better. Overzealous in her cross-questioning and habitually alienating the jury, Singer seems to hurts cases more than she helps. However, she wins a lot of her cases, although many people suspect that she uses less-than-legal methods to do so for some of them. She was recently transferred to the USS Seahawk, but was sent back when it was discovered she was pregnant. Her current status is deceased.
Commander Sturgis Turner (played by Scott Lawrence): An old friend of Harm's from the Academy, Sturgis recently joined JAG as a senior lawyer. A very good lawyer and a good man, he has much to offer to the JAG team. Recently, though, he came under investigation regarding his ability as a lawyer and then was accused of being racially biased against Koreans. However, the storm seems to have subsided for the moment.
Petty Officer, First Class, Jason Tiner (played by Chuck Carrington): Tiner was Admiral Chegwidden's personal yeoman, helping the Admiral plan parties, schedule appointments, control the flow of people in and out of the Admiral's office, and much much more. A very valuable member of the JAG team for quite some time, Tiner eventually left JAG HQ to become a Navy lawyer. His position as yeoman was taken over by Petty Officer Jennifer Coates.
(Episodes Tiner has appeared in)
Dr. Sydney Walden (played by Cynthia Sikes): A serious love interest of Admiral Chegwidden, Dr. Walden was introduced to the Admiral, after an embarassing incident, by her good friend Mac. While they hit off extremely well, at first, they were driven apart when they took opposite sides after her son wrecked the Admiral's car.
(Episodes Dr. Walden has appeared in)
Clayton "Clay" Webb (played by Steven Culp): Born in 1962, Clayton Webb worked for the NSA then the CIA. He followed in his father and mother's footsteps, became a director at the CIA. He often got Harm and Mac into trouble and was actually responsible for them being partnered together. His current status is deceased, although he has faked his death before.
(Episodes Webb has appeared in)
Sergei Zhukov (played by Jade Carter): A former sergeant in the Russian army, Sergei is Harm's half-brother.
(Episodes Sergei has appeared in)
In order to not give away too many spoilers, I have not included much information from the time during the episodes.