During 1962, he married Seema Silberstein, the daughter of a Detroit real estate magnate whose holdings included The Beverly Hills Hotel in California. After his father-in-law's death, Boesky and Seema won a court battle with her sister and brother-in-law over the hotel's ownership.
In 1966, Boesky and his wife relocated to New York where he worked for several stock brokerage companies. During 1975, he initiated his own stock brokerage company, Ivan F. Boesky & Company, with $700,000 (equivalent to $3.3 million in 2018) worth of start money from his wife's family with a business plan that speculated on corporate takeovers. Boesky's company grew from profits as well as buy-in investments from new partnerships. By 1986, Boesky had become an arbitrageur who had amassed a fortune of more than US$200 million by betting on corporate takeovers and the $136 million in proceeds from the sale of The Beverly Hills Hotel. Boesky was on the cover of Time magazine December 1, 1986.
During 1987, a group of partners sued Boesky over what they claimed were misleading partnership documents. The U.S. Securities and Exchange Commission investigated him for making investments based on information received from corporate officers. These stock acquisitions were sometimes brazen, with massive purchases occurring only a few days before a corporation announced a takeover.
Boesky, unable to rehabilitate his reputation after being released from prison, paid hundreds of millions of dollars as fines and compensation for his Guinness share-trading fraud role and a number of separate insider-dealing scams. Later, Boesky began practicing Judaism and attended classes at the Jewish Theological Seminary of America where he had been a major donor; however, during 1987, after the fallout from his financial scandal, The New York Times reported that "after Ivan F. Boesky had been fined $100 million in the insider-trading scandal, the Jewish Theological Seminary, acting at his request, took his name off its $20 million library."
In a 2012 interview with The New York Times, a cousin of Boesky's disclosed that he is living in La Jolla, California.
During 1991, he divorced his wife and she agreed to pay him $23 million and $180,000 a year for life. They have four children.
In the novel American Psycho (1991), Craig McDermott wins a Halloween costume party dressed as Ivan Boesky.
In Gump & Co. (1995), the sequel to Winston Groom's novel Forrest Gump (1986), the protagonist Forrest Gump was hired by "Ivan Bozosky". Gump also later begins to wonder how he is able to command such a high salary for only having to sign papers.
A 1989 issue of MAD had a spoof of baseball cards featuring celebrities, one being Boesky wearing an old-style black and white prisoner's uniform and using his ball from the "ball and chain" akin to pitching a baseball with the caption "Bats left, steals left and right". The issue debuted soon before Boesky's release.
Another version of these events is recounted by Jonathan Guinness in his book Requiem for a Family Business which suggests the SEC granted him immunity from prosecution and allowed him to continue to insider trade for significant profit whilst wire tapping him to gain evidence against others.
In an episode of The Golden Girls titled "Love for Sale" (1991), Rose Nylund tells Dorothy Zbornak that her late husband Charlie once made a lot of money with a business partner who was "a no good, underhanded backstabbing worm", which Dorothy responds "Let me guess Rose, Ivan Boesky-Vanderfloovenhoover-meistergarbengerbenfleckman".
In an episode of Animaniacs titled "Plane Pals" (1993), Yakko, Wakko, and Dot harass a tightly-wound Wall Street accountant named Ivan Blowsky, when he is forced to sit next to them on an airplane.
Boesky is mentioned in the episode "Last Days" of the television series Sliders: after an asteroid fails to destroy the Earth of the dimension they are in, Rembrandt Brown sees an article in a newspaper stating that Boesky had bought half of the houses in Beverly Hills for $10,000 dollars apiece, and that the erstwhile owners want their houses back.
In the episode "Psy vs. Psy" of the television show Psych, Boesky is mentioned by a federal agent during a masculinity contest. With him specifically saying "I personally arrested Ivan Boesky."
In season 2, episode 15 of the American sitcom Murphy Brown, "Subpoena Envy", which aired in January 1990, when Murphy is teased for being sent to a minimum-security prison rather than to a more dramatic-looking facility for protecting the identity of a witness, she says, "Hey! I'm sorry! How do you think I feel? I'm sitting here with the committee to free Ivan Boesky!"
In the Futurama episode Future Stock, production number 3ACV21, Boesky is mentioned by a character from the 20th century. The character being a stock trader says, "Back in the 1980s, I was the toast of Wall Street. I was having whiskey with Boesky and cookies with Milken. But then, I was diagnosed with terminal boneitis."