The company was founded by Dick Portillo on April 9, 1963, in Villa Park, Illinois, under the name "The Dog House".

[5] After returning from serving in the Marines, Portillo gathered money from his savings and an investment from his brother Frank to open a hot dog stand.

By 1967, The Dog House, now in good financial standing, was upgraded to a larger trailer and was renamed "Portillo's".

[12] Its initial public offering sold 28% of the company as stocks traded on the Nasdaq as of October 21, 2021, with private equity firm Berkshire Partners retaining the remainder of the ownership.

The chain generated publicity with a tongue-in-cheek open letter on its website on June 16, 2015, the day after its hometown NHL team, the Chicago Blackhawks, beat the Tampa Bay Lightning to win the 2015 Stanley Cup.

So we're thrilled we're finally making our way to Florida," Portillo's letter said, showing the chain's ironic humor.

Shortly thereafter in early fall 2017, the chain's first restaurant in the Indianapolis metropolitan area commenced operations in Fishers.

In 2018, Portillo's opened its second and third restaurants in the Minneapolis-St. Paul area (Maple Grove and Roseville, Minnesota)[18] as well as its third and fourth Indiana locations (Mishawaka and Indianapolis)[19][20] in 2018.

[23] In December 2021, Portillo's submitted plans to build a new restaurant at Santan Village in Gilbert, Arizona.

It is located in the Dallas Fort Worth Metroplex suburb of The Colony, at the intersection of SH 121/Sam Rayburn Tollway and Destination Drive at the Grandscape complex.

In March 2024, the company announced it would open two new restaurants in the Houston area—one in Richmond at The Grand at Aliana and the other at the Willowbrook Mall.