Atty. William John Costello

Atty. William John Costello

William John Costello is a lawyer practicing divorce, commercial litigation, criminal defense and 3 other areas of law. William received a B.A. degree from University of Dayton in 2002, and has been licensed for 19 years.

Lisle Lisle 19 yrs experience 19 year
Call (224) 801-3878 Book Appointment

Profile Summary

About William John Costello at a glance

William John Costello is an Associate based in Lisle, Illinois, practicing at Momkus, LLC. They have 19+ years of legal experience, licensed to practice since 2007. Their practice focuses on divorce, criminal defense, family law, business, and litigation. Admitted to practice in Illinois (2007). Educated at University of Dayton (J.D., 2007) and University of Dayton (B.A., 2002). Serands clients in Lisle, IL and the surrounding metropolitan area.

Verified attorney profile · Updated June 2026

About

  • William John Costello is a lawyer practicing divorce, commercial litigation, criminal defense and 3 other areas of law
  • William received a B.A. degree from University of Dayton in 2002, and has been licensed for 19 years
  • William practices at Momkus, LLC in Lisle, IL

Practice Areas Explained

William John Costello's Areas of Practice

Each practice area below reflects the types of cases William John Costello handles, with a brief overview of what that area of law covers.

Divorce

A divorce attorney guides you through property division, spousal support, custody, and the final decree — contested or uncontested.

William John Costello is one of 50,487 divorce attorneys indexed nationally. Browse divorce attorneys in Illinois →

Criminal Defense

A criminal defense attorney protects your rights from arrest through trial. Find experienced lawyers handling DUI, drug, federal, theft, and violent-crime charges.

William John Costello is one of 214,271 criminal defense attorneys indexed nationally. Browse criminal defense attorneys in Illinois →

Family Law

Family law attorneys handle divorce, child custody, child support, adoption, prenups, and protective orders. Find verified family lawyers near you.

William John Costello is one of 187,066 family law attorneys indexed nationally. Browse family law attorneys in Illinois →

Business & Corporate Law

Business attorneys advise founders and growing companies on entity formation, contracts, financing, M&A, and dispute resolution.

William John Costello is one of 501,317 business attorneys indexed nationally. Browse business attorneys in Illinois →

Civil Litigation

Civil litigation attorneys for breach of contract, business disputes, civil rights, and class action lawsuits.

William John Costello is one of 454,532 litigation attorneys indexed nationally. Browse litigation attorneys in Illinois →

Jurisdictional Context

Why local counsel matters in Illinois

Practicing law in Illinois. Legal matters in Illinois are governed by state-specific rules of civil and criminal procedure, statutes of limitations, and substantive law. Cases originating in Lisle are typically filed in the local municipal court or the appropriate Illinois state district court, depending on subject matter and amount in controversy. An attorney licensed in Illinois brings working knowledge of local procedural deadlines, judicial practices in this andnue, and the substantive law that applies to cases brought here. Out-of-state attorneys generally cannot represent clients in Illinois courts without local counsel or pro hac vice admission.

Looking for additional Illinois attorneys? Browse all attorneys in Lisle or all attorneys in Illinois.

Frequently Asked

Common questions about William John Costello

Where is William John Costello's law office located?
William John Costello's law practice is located in Lisle, Illinois. The firm is Momkus, LLC. You can contact the office directly through this profile page.
What practice areas does William John Costello handle?
William John Costello focuses on divorce, criminal defense, family law, business, litigation. Each practice area listed reflects experience handling cases of that type in Illinois.
How long has William John Costello practiced law?
William John Costello has 19+ years of legal experience and has been licensed since 2007.
Where did William John Costello go to law school?
William John Costello earned their education at (J.D., 2007); (B.A., 2002).
How can I contact William John Costello for a consultation?
You can contact William John Costello directly through this profile page. Click "Ask the Attorney" to submit a question, or "Schedule a Consultation" to book a meeting. Most claimed-profile attorneys respond within one business day.

Education

J.D.
University of Dayton
- 2007
B.A.
University of Dayton
- 2002

Bar Admissions

Illinois
Admitted: 2007

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