The second season of the American television drama series Mad Men premiered on July 27, 2008, and concluded on October 26, 2008. It consisted of thirteen episodes, each running approximately 48 minutes in length. AMC broadcast the second season on Sundays at 10:00 pm in the United States; it would occupy in this timeslot for the remainder of its run.

Season two takes place from February 14 to October 24, 1962, culminating with the Cuban Missile Crisis. It expands on Peggy's rise in the workplace and the marital strife between Don and Betty Draper as Don's infidelities further intrude on his family life. The second season also introduces an unknown acquaintance, with whom Don is corresponding by letter in secret.

The second season of Mad Men was met with critical acclaim: it was honored with the Primetime Emmy Award for Outstanding Drama Series, the Golden Globe Award for Best Drama Series, and recognition by the American Film Institute, all for the second year in a row. According to Metacritic's annual aggregate of year-end lists published by prominent television critics, Mad Men was the most mentioned show of 2008, with more first-place mentions than any other show that year as well.

Season two opens on Valentine's Day, 1962, fifteen months after the events of season one. The Draper marriage seems to be on sturdier footing, while Peggy has returned to work. Joan and Roger have ended their romance. Betty has taken up horseback riding as a hobby and rebuffs the constant flirtations of a male fellow rider, Arthur Case.

Sterling Cooper travels further into the "Pepsi Generation" as signing youth talent becomes a priority at the behest of "Duck" Phillips, Draper's choice as head of accounts from the previous year. Duck then convinces the firm to try and sign his old client, American Airlines, after the airline publicly announces a shift in marketing. Draper protests, as pitching for the project requires the firm to drop Mohawk Airlines, one of Draper's main clients. The American Airlines pitch fails, significantly harming Phillips' reputation at the firm and creating palpable tension with Draper.

Joan, having been outed to her coworkers by Paul as being 31 years old, hurriedly becomes engaged to egotistical and frustrated medical resident Greg Harris. Too proud to admit to his own insecurities regarding his career, Greg takes full advantage of being the only man Joan is willing to be submissive to; this culminates in him raping Joan inside Don's office prior to the couple's wedding. In spite of this, Joan remains with her fiancé.

As fellow creative Freddy Rumsen devolves into alcoholism, Don has to step in to handle the obnoxious antics of his talent, comedian Jimmy Barrett, and ends up having an extramarital affair with Barrett's wife, Bobbie. Don's relationship with Bobbie is significantly more volatile than his past affairs. After Don discovers that Bobbie and other women around town have been discussing Don's sexual prowess, Don leaves her tied to a hotel bed in her lingerie. Later, a resentful Jimmy tells Betty about the affair, eventually causing her to kick Don out of the family home.

Peggy, meanwhile, strikes up a courteous friendship with her priest, Father Gill. Peggy's sister tells Father Gill about Peggy's previous pregnancy during confession, which he subtly reveals to Peggy. Flashbacks to January 1961 reveal that Don was Peggy's only visitor at the hospital after her child was born. Don had convinced her to get out of the hospital and return to work, telling her, "This never happened. It will shock you how much it never happened."