About Us


After working together to serve the people of Illinois for more than eight years as prosecutors in the State’s Attorney’s Office in Cook County, Peter O’Mara and Sean O’Callaghan joined together in 2013 with a vision for a different kind of law firm.

Today, the firm of O’Mara & O’Callaghan takes a collaborative and honest approach to counseling and litigating for our clients.


We are leaner, more responsive, and more aggressive than other law firms.

Our model is designed to resolve disputes for businesses and individuals in the timeliest and most cost-efficient manner possible. We find the quickest path to victory and pursue it vigorously for our clients. While avoiding trial is frequently the best business decision, we are not afraid to take a case into the courtroom – and we know how to win when we are there.

With our collective experience litigating hundreds of trials and hearings, we have an unmatched perspective on the steps necessary to avoid disputes. As trial attorneys, we draft all documents with an eye toward avoiding potential litigation. We anticipate where each contract’s terms are most vulnerable to a potential dispute and address those issues thoroughly during drafting.


We believe it is a law firm’s duty to provide value in every client interaction, a goal that can be achieved only with a transparent billing process.

Since not all legal matters are the same, they should not be billed in the same way. We model our billing methods on our client’s preferences to ensure that each client achieves their definition of value.

Clients often come to us after becoming frustrated with large law firms. A 2016 Crain’s Chicago Business study showed hourly rates at Chicago’s largest law firms ranging from $470 to more than $1200 an hour for litigation and from $575 to more than $1300 for business counseling.

Clients who come to us after using the big firms say that they initially felt compelled to hire a large firm because of a perception that larger firms have deeper experience and greater legal skill. These business owners and individuals become discouraged, however, by larger firms’ unwillingness to move aggressively and reluctance to litigate – as well as by endless legal bills and wheel-spinning.

After coming to us, clients quickly find that the legal services we provide surpass what they received from larger firms in many ways.

We are proud that clients return to us time and again to protect and grow their businesses.