About Our Firm
Shaheen Guerrera & O’Leary are not only the attorneys you need now, but the attorneys who can and will be with you in the future. SGO is a full-service law firm able to support you through the legal issues you will face in your lifetime.
SGO has over 100 years combined experience and a resume of diverse legal specialties. What does this mean for you? Together SGO provides clients like you with the exact counsel you need, right when you need it.
Peter Shaheen, Sean O’Leary and Nicholas Guerrera all have firm ties to the local community and extensive experience with both the State and Federal courts of Massachusetts and New Hampshire. They have established relationships with business leaders and legal colleagues through both states and beyond.
Business Law to Family Law. Estate Planning. Real Estate Law. Personal Injury. Civil Rights Law. No matter your legal need, you have a partner here at SGO.
Our Practice Areas
Business Law
Contracts, Merger & Acquisition, Governance and Dissolution, Employment Law and more.
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Who We Are
Our History
SGO has over 100 years of legal experience in both Massachusetts and New Hampshire. They have an extensive understanding of the local legal landscape, and a personal investment in the community too: Peter, Nicholas, and Sean all reside in the Merrimack Valley with their families.
Our Mission
SGO strives to be accessible to clients and recognizes the personal nature of each individual case. Beyond their legal expertise, they apply their own personal and life experience as community leaders, business, and property owners to further enhance their understanding of their clients’ needs.
Our Vision
SGO is focused on developing positive relationships with clients and providing them with the best solution for their unique case. They are proud of their ability to serve their clients successfully now and to maintain that partnership well into the future.
Our Partners
Nicholas S. Guerrera
Partner
Peter G. Shaheen
Partner
Sean P. O’Leary
Partner
What Our Clients Are Saying
Mom of 2, Essex County
If you seek an empathetic, expert and fiercely detailed professional to mediate your divorce, I wholeheartedly recommend Sean O’Leary. I reflect on our process with admiration and relief that there are people like Sean watching out for our families through the hardest times. Sean will actively listen and strategize with his clients, and will tirelessly yet efficiently consider all possibilities for your particular circumstances. He is adept at facilitating conversations between people with differing communication styles, keeping everyone on the same page and focused on the end result. In our case, his cultural competency and kindness were additional assets that enabled him to bring diverse clients to the best possible outcome for every member of our family. Sean O’Leary is the person you want steering your ship through what can feel like a storm; he will help navigate you to the calmest waters for the long-term.
Donna, Essex County
I walked into the law office of Sean O’Leary approximately 16 years ago, looking for an honest lawyer to help me navigate the challenges of a divorce. What I found was so much more than that. Sean was and is factual, knowledgeable, detailed, kind, and honest. His efficiency has supported me though all these years with my divorce, the creation of my will and my trust, and the review of my pension. I have never and will never hesitate to reach out to Sean because I know he has the expertise to handle everything that I throw his way. My questions are answered quickly and the information I receive is consistently beneficial. Sean always has my best interest at heart and he will have yours also. If you want the best I highly recommend you hire Sean O’ Leary.
Mom of 3, Essex County
I recently went through a difficult divorce that lasted for three long years, and I couldn't have navigated through it without the exceptional legal representation provided by Sean O’Leary. As a 48-year-old woman facing the complexities of divorce proceedings, I was initially unclear about my rights and unsure about how to handle the situation fairly with my ex-spouse. However, Sean proved to be an invaluable asset throughout the entire process. From our very first meeting, I was impressed by Sean's professionalism, knowledge, and dedication. He took the time to listen attentively to my concerns, providing a safe and supportive environment where I felt comfortable discussing the details of my situation. His ability to empathize and understand the emotional toll of a divorce was truly remarkable, and it made a world of difference in my experience. Not only did Sean demonstrate exceptional legal expertise, but he also guided me through the legal proceedings with utmost care and consideration. He was always available to address any questions or doubts I had, promptly responding to my calls and emails. His attention to detail and thoroughness in explaining the legal intricacies ensured that I was well-informed and prepared at every step. I cannot overstate how grateful I am for the substantial cost savings achieved through Sean’s expertise. He skillfully navigated the complexities of the legal system, effectively advocating for my rights while ensuring unnecessary expenses were minimized. His strategic thinking and negotiation skills were evident throughout the process, resulting in a favorable settlement that exceeded my expectations. In addition to his legal acumen, Sean exhibited exceptional professionalism and integrity. He consistently maintained clear and transparent communication, providing regular updates on the progress of my case. His ability to convey complex legal concepts in a manner that was easy for me to understand was greatly appreciated. Overall, I wholeheartedly recommend Sean O’Leary to anyone in need of a compassionate and knowledgeable attorney. His unwavering support, expertise, and genuine concern made a significant impact on my journey through divorce. I am truly grateful for his guidance, and I am confident that he will continue to help others navigate through challenging legal situations with the utmost skill and care. Thank you, Sean, for all that you have done for me. You have made a positive difference in my life during an incredibly challenging period, and I will forever be grateful for your exceptional representation.
Mark, 2 children
After 22 years of marriage, I needed an outstanding attorney. I had gone through three others until I met Sean O’Leary. He is outstanding. He is a family man whose wife works in the office as well. He has your best interest at heart. He’s a no nonsense guy. He became a friend over the several years I needed his advice. He always made sure to look out for my best interest. I couldn’t ask for a better attorney than Sean was and got me the most reasonable and adequate deal possible. I would highly recommend Sean and his firm. If I ever need assistance again, I will definitely go to Sean for his expertise and advice.
Julie, 2 adult children
Sean is extremely thorough, organized and detail-oriented in all aspects of the collaborative divorce process. He explained everything to me in clear language and made sure I understood the implications of any decision. He has a calm demeanor, is patient and respectful to all parties. Sean really took the time to get to know me and understand my situation and was always looking one step ahead to make sure we were prepared. His approach, and his skill and experience as an attorney, helped me achieve the best possible outcome. I would highly recommend Sean to represent anyone in a collaborative divorce proceeding.
– Paul W. George
President, Custom Modular Homes of New England, Inc"I chose Peter Shaheen as my attorney because he has a great deal of small business practicality and knowledge. When assisting me in making legal decisions, he not only utilizes the logistical background of an attorney but also as a business owner. He has developed a support staff that is by far the best I have ever worked with in a law office."
– Paul A. Marchionda
President, Marchionda & Associates, Inc"I have been doing business with Attorney Shaheen both personally and professionally for over 30 years. In addition to providing expert legal advice and representation, Peter and his associates have a great common sense approach to addressing all of your needs which is a rare quality not found in many law firms."
– Jane Hughes
General Partner"Peter Shaheen’s sensitivity to the unique issues facing asmall family business, as it transitions from one generation to the next, was critical in helping me make good decisions for our operations. I appreciate his flexible thinking, his well-timed tenacity and his sense of humor in what has not always been a very pleasant process. I look forward to calling upon Peter for legal advice whenever the need should present itself in the future."
– James M. Coskren
C.I.L., Inc"From a personal and business perspective the experience, knowledge and guidance of Attorney Peter Shaheen and his staff provides me the direction I need to make sound decisions."
Partnerships
