Of American-English origin, the phrase (it) takes one to know one means that only a person with a given personality, characteristic, etc., is able to identify that quality in someone else—cf. note.

Like the pot calling the kettle black, this phrase is typically used as a retort by a person who has been criticised or insulted, to suggest that the criticism or insulting remark applies equally to the person who made it.

The earliest occurrence that I have found is from the beginning of an article by Kathryn Kenney, published in the Camden Post-Telegram (Camden, New Jersey, USA) of Wednesday 20^th January 1926:

Woman Is Having Her Innings And At Present Outings Also
Father Is No Longer Only Member of Family to Step on Cat’s Tail and Hold Clock’s Hands at Four O’Clock in Morning—Mamma Checks in Later

Women are at last having their day and a goodly number are biting off a generous portion of the evening.
Father no longer is the only member of the family to step on the cat’s tail and hold the clock’s hands at 4 in the morning. Mother has quit being a burden to her dancing partner and the night cap is off the shingle.
In the old [d]ays when father went to the lodge meetings or to sit up with some other sick friend he was fairly certain that the little woman would be holding down the haircloth sofa and knitting him bed socks. Now he wonders who is helping her hold it down and he hurries home to take thumb prints. It takes one to know one, or words to that effect.
Woman has at last recognized the fact that the only thing which will bring a man home early is curiosity. He leaves his party on a dead run to save the cost of a detective.

The second-earliest occurrence that I have found is from the beginning of an article by Rupert B. Turnbull, published in MoToR BoatinG: The Yachtsmen’s Magazine (New York: International Magazine Company, Inc.) of July 1935:

Invitation for Los Angeles Hearst Gold Cup Regatta ¹

This is a daffy draft from a devilish, delirious, happy heart, rising to adventure. The adventure is the Hearst Gold Cup Regatta for outboard motor boats July 21, 1935. The author is happy because he has been unanimously selected by the motor boat clubs here in the Southland, as well as the Los Angeles Examiner and William Randolph Hearst, to be general manager and commodore for the day for this event.
Some people don’t like me because they say I am a show-off. Applying the old saying, “it takes one to know one,” I am personally inviting you and your boat, your helmet, goggles and red life jacket, to participate. The occasion demands highly flavored, robust, noisy jollification. Let’s put on a show! Let’s—have a great party, a real water carnival!

¹ The U.S. businessman, newspaper publisher and politician William Randolph Hearst (1863-1951) was President of the International Magazine Company, Inc., and sponsor of the annual Gold Cup Regatta.

The phrase may have been borrowed into British English through U.S. television series, since all the earliest occurrences that I have found of it takes one to know one in British publications are as follows:
– the title of an episode of Bewitched ², broadcast on BBC TV on Monday 11^th January 1965;
– the title of an episode of It Takes a Thief ³, broadcast on ITV on Monday 16^th September 1968;
– the title of an episode of Get Smart ⁴, broadcast on BBC One on Monday 3^rd February 1969.

² The U.S. comedy television series Bewitched (1964-72) starred Elizabeth Montgomery (1933-1995) as Samantha Stephens and, originally, Richard York (1928-1992) as Darrin Stephens, her husband.
³ The U.S. action-adventure television series It Takes a Thief (1968-70) starred Robert Wagner (born 1930).
⁴ The U.S. comedy television series Get Smart (1965-70) starred Don Adams (Donald James Yarmy – 1923-2005) as agent Maxwell Smart (Agent 86) and Barbara Feldon (born 1933) as Agent 99.

In the USA, the phrase is particularly used of male homosexuals. For example, the following letter appeared in the advice column written by Ann Landers (pen name of Esther Pauline ‘Eppie’ Lederer (née Friedman – 1918-2002))—published in the Waukesha Freeman (Waukesha, Wisconsin, USA) of Monday 27^th December 1971:

Ex-Homosexual Says: It Takes One to Know One
Dear Ann: I am what is clinically referred to as “bisexual.” I prefer to think of myself as an ex-homosexual. […]
[…]
This letter is to reinforce something I read recently in your column. You said “homosexuals have a built-in radar for detecting their own kind.” You are 100 per cent right. Although I’ve had no sexual contacts with a male for 12 years, I can spot a gay boy a block away no matter how straight he looks to the uninitiated.

And, on Sunday 15^th October 1972, The Post-Crescent (Appleton, Wisconsin) reported Dr. Darold A. Treffert, Superintendent of Winnebago State Hospital, a psychiatric hospital near Oshkosh, Wisconsin, as saying that studies in the area of homosexuality

haven’t been very good up this point, largely due to the fact that researchers have tended to steer away because of the idea that ‘it takes one to know one.’

 

Note: (it) takes one to know one is therefore similar to the following earlier phrases:

– set a fool to catch a fool, used by Edmund Gayton (1608-1666) in Pleasant notes upon Don Quixot (London: Printed by William Hunt, 1654):

The whimsy of the Knight, is to be cured with another whimsy, as they say, set a fool to catch a fool; a Proverb not of that gravity (as the Spaniards are,) but very usefull and proper.

– set a thief to catch a thief, recorded by John Ray (1627-1705) in A Collection of English Proverbs (Cambridge: Printed by John Hayes for W. Morden, 1670). This phrase also appeared in The Committee (London: Printed for Henry Herringman, and are to be sold by R. Bentley, J. Tonson, F. Saunders, and T. Bennet, 1692), a comedy by Robert Howard (1626-1698):

According to the old saying,
Set a Thief to catch a Thief.