Principal

Daniel M. Costello

Daniel’s portfolio includes both transactional and civil litigation representing both individuals and businesses. His practice includes a robust community association practice (cooperatives, condominiums and homeowners associations), landlord and tenant practice, and general litigation and collection services.  Daniel helps board members achieve the community’s goals while adhering to the governing documents and relevant laws.  Daniel enjoys teaching and collaborating with boards by explaining how the law applies, and what it means for the association’s operations. He also works with community associations to draft rules and regulations, amend governing documents, enforce the governing documents, collection of assessments and planning for aging infrastructure.

When a matter cannot be resolved, Daniel represents clients in litigation. Daniel will strategically pursue the best outcome for his clients’ needs and will work with his clients to ensure that they understand their options and how the case will proceed. Daniel has represented clients in breach of contract, construction defect, tort, estate and other litigation matters. Most recently, he successfully represented a hotel in a breach of contract claim related to construction and remodeling defects. Prior to opening the firm, Daniel worked for a large regional law firm, known for its community association practice and litigation services.

Daniel is a native Washingtonian and obtained a Bachelor of Arts degree in Philosophy, Classics, and Religion from the University of Mary Washington. He graduated cum laude. Daniel attended the George Washington University Law School where he obtained his Juris Doctorate. Daniel was admitted to the Maryland Bar in 2009 and the District of Columbia Bar in 2010. To support his expanding practice, Daniel was admitted to the Virginia Bar in 2017. Daniel is currently authorized to practice before the following courts:

· District of Columbia Superior Court and Court of Appeals
· United States District Court for the District of Columbia
· United States District Court for the District of Maryland
· Maryland Court of Appeals  
· Maryland District and Circuit Courts
· Supreme Court of Virginia
· Virginia District and Circuit Courts

Reported Opinions Weatherly v. Second Northwest Coop. Homes Assoc., Inc.

Of Counsel

Jessica S. Blumberg 

Jessica is the firm’s lead attorney for civil litigation and arbitration throughout Maryland and the District of Columbia. Jessica brings her tenacious and thoughtful energy into every case. She also appreciates the importance of balancing dauntless advocacy and clients’ goals. This has earned Jessica the respect of both her clients and opposing parties and counsel.  Jessica represents clients on matters involving construction defect, landlord and tenant disputes, breach of contract, and tort claims.  Additionally, Jessica represents parties that are part of cooperative associations, condominium associations, and homeowners associations, including individual persons or the Board of Directors. 

In 2022, Jessica successfully argued before the Maryland Court of Special Appeals regarding a dispute between a homeowners association and an owner concerning a fence encroachment. You may view her oral argument here. A copy of the opinion is also available here.  Jessica was also interviewed and featured on ABC 2’s Matter for Mallory regarding this fence dispute. The article and interview may be viewed here.

Jessica grew up in New York, and is passing onto her son the joys of being a Mets’ and Jets’ fan. She obtained a Bachelor of Arts, magna cum laude, from Brandeis University and her Juris Doctorate, cum laude, from American University Washington College of Law. Following law school, Jessica clerked for the Honorable Cynthia Callahan for the Circuit Court for Montgomery County, Maryland. Prior to joining Costello PC, Jessica was a litigator at a boutique law firm and a large regional law firm in the DC area, and by age 30 was recognized as one of the best under 40 in her field in Bethesda Magazine.  Jessica was selected as a Rising Star in Maryland and D.C. by Super Lawyers in 2017, 2018, 2022, 2023 and 2024.

Jessica is currently authorized to practice before the following courts:

· District of Columbia Superior Court and Court of Appeals
· United States District Court for the District of Columbia
· United States District Court for the District of Maryland
· Maryland Court of Appeals  
· Maryland District and Circuit Courts

Reported Opinions Weatherly v. Second Northwest Coop. Homes Assoc., Inc.

Education

• Brandeis University

• American University Washington College of Law

Email: Jessica@costellopc.com

Direct: 202-239-2261

Activities & Affiliations

• Maryland Bar Association

• District of Columbia Bar Association

• Book Buddies Reading Tutor for Alexandria Tutoring Consortium

• Editorial Advisor for Greet Del Ray Magazine

Attorney

Now Hiring 

Send Resume to daniel@costellopc.com

Education

• University

• University

Email: @costellopc.com

Direct: 202-239-2257

Associate

John O’Reilly

John is an associate attorney practicing in the District of Columbia and Maryland who brings a client-centered approach to every matter. He has represented clients across a broad range of civil litigation matters, including high-stakes and complex disputes. He routinely drafts motions, pleadings, discovery demands, legal memoranda, and settlement agreements, and has argued numerous matters in court.

John grew up in New Jersey and now resides in Washington, DC. He earned his Juris Doctor from Rutgers Law School, where he was a member of the International Law & Human Rights Journal, and he holds a Bachelor of Science, cum laude, from High Point University. John is admitted to practice in the District of Columbia. Maryland and New Jersey.

John is currently authorized to practice before the following courts:

· District of Columbia Superior Court and Court of Appeals
· Maryland Court of Appeals  
· Maryland District and Circuit Courts

Education

• High Point University

• Rutgers Law School

Email: John@costellopc.com

Direct: 202-239-2873

Legal Secretary and paralegal

Diane Lewis

Diane serves as both a legal secretary and paralegal for Costello, P.C. She supports the attorneys and other staff at the firm. Her dedication and strong analytical skills are an asset to the practice. She brings years of experience to the firm from working at other regionally recognized law firms.

Diane enjoys spending time outdoors, and her interests include working in her garden in the spring and summer months, enjoying an annual trip to North Carolina’s Outer Banks with close friends, frequent travel to exciting destinations, various forms of exercise, and spending time with her family.

Education

• Diane attended Frederick Community College in Frederick, MD.

  Email: dlewis@costellopc.com

  Direct: 202-239-2649