Marcus Boyd, a young African-American, has recently graduated from Columbia Medical School and is going to Laos for a year to work with Doctors Without Borders. Lucia Ramirez, who is Mexican-American, volunteers at a charter school for recent immigrants as an English teacher, having dropped out of Columbia Law School to pursue her passion, although she has neglected to tell her parents. Unbeknownst to their respective families, they have been living together for several months and are planning to wed before going to Laos together.

Meanwhile, in Los Angeles, Marcus' father Brad, a successful radio host, is returning from a typical one-night-stand with a younger woman when he sees his car being towed by Miguel, who happens to be Lucia's father and runs a successful auto shop and towing business. Brad tries unsuccessfully to halt the tow by holding on to the door of his car. Both Miguel and Brad hurl various racial insults at one another. That night, Marcus and Lucia invite their families to a joint dinner, where Miguel is surprised to learn of Marcus's existence, and Brad brings a much younger date who is in fact an old high school friend of Lucia's. As a shock to both families, the couple reveal their engagement and travel plans, with Brad and Miguel incredulous that they will soon be in-laws. As the wedding planning begins, both families attempt to dominate it with their respective traditions, while Brad's long-time friend Angie helps to mediate things, stressing the phrase "Our marriage, their wedding" to Marcus and Lucia to help them understand how much they must compromise to keep peace between their loved ones.

The wedding is set to take place at Brad's estate, much to his chagrin, and Brad tries to dissuade Marcus from rushing into a marriage as he feels he did with Marcus's mother. Meanwhile, Miguel feels that Marcus is not good enough for Lucia because she did not feel comfortable enough to mention him before the engagement. While wedding dress shopping, Lucia's sister Isabel, who helps run the auto shop with Miguel, argues with Lucia about marrying young like the other women in their family, something they vowed not to do as teenagers. Their mother Sonia overhears their conversation, which quickly shifts to mocking her life as a homemaker who is clearly living vicariously through the wedding, which upsets her.

While trying to hire a DJ for the reception, Miguel and Brad become drunk at a club and are arrested after an altercation. When Marcus and Lucia go to pick them up from the station, an argument erupts in which Miguel feels that Marcus is freeloading off of Lucia since he will be working as a doctor without pay and still believes that she is becoming a lawyer. When Lucia does not come to his defense, Marcus feels abandoned, leading to another argument between them. When Lucia questions if Marcus still wants to get married, he replies "I don't know", which leads her to call off the nuptials. Angered when Sonia refers to the wedding as "our wedding" and Miguel offers to "toss the ball" at the news, Lucia finally admits all the secrets she has been keeping from her parents, leaving them shocked.