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William Michael Sullivan

William Michael Sullivan

Practice areas:

Family, Divorce & Separation, Marriage & Prenuptials

About Me

Matrimonial and Family Law matters can be some of the most challenging experiences an individual must go through in life.  Unfortunately, the stakes are very high as they often involve matters that will affect the lives of your children for many years to come.  It is for this reason that you must consider a law firm with significant experience in the fields of Matrimonial and Family law.  Equally, due to the complexity of these matters, you must consider a full service law firm, such as ours, which maintains partners practicing in a vast array of legal disciplines such as coporate, real estate, taxes, etc. such that the firm is equipped to handle the numerous ancillary issues that come with Matrimonial and Family Law matters.  When choosing a law firm, It is essential that they have a superior knowledge of the law, an understanding of the many day-to-day demands placed upon a family as they go through this process, coupled with a sensitivity to the fact that resources are better spent on "college funds" than litigation.  Client satisfaction and effective, effecient representation is our paramount concern.  Our firm has spent decades refining our skills in each of these facets and will serve you well.


Practice Areas

Licensed since 1992

  1. Divorce & Separation: 40%
    15 years
  2. Family: 40%
    15 years
  3. Marriage & Prenuptials: 20%
    15 years



Hourly ($200-450/hour), Retainer (Always)

Payment Types:

Cash, Check, Credit Card

Attorney Endorsements

3 total 

  • No photo

    Ms. Sullivan is highly respected by his colleagues for his professional conduct, intelligence and tenacious representation of his client.


    Catherine Miller Divorce & Separation Attorney
    Relationship: Fellow lawyer in community

  • Karen Svendsen

    I endorse this lawyer. Mr. Sullivan is an extremely tough and competent litigator who stops at nothing to pursue the rights of his clients. In addition, Mr. Sullivan has integrity and always treats his clients with the utmost respect and personal attention. I highly recommend this attorney for any Family Law matter.


    Karen Svendsen Divorce & Separation Attorney
    Relationship: Co-worker

Contact Info

Long Tuminello, LLP

120 4th Ave
Bay Shore, NY, 11706-7938


NYCurrently registered 199203/13/2015

Professional Misconduct

We have not found any instances of professional misconduct for this lawyer.
Avvo Contributions
Legal Answers
Award NameGrantorDate Granted
Top Attorneys in Long IslandLegal Leaders2014
Trial AdvocacyVillanova University School of Law1992
Moot Court BoardVillanova University School of Law1991

Work Experience
TitleCompany NameDuration
PartnerLong Tuminello, LLP2003 - Present
Managing PartnerWilliam M. Sullivan, P.C.2001 - 2003
General Counsel/Director of ComplianceAMBAC Financial Services, Inc.1992 - 2001

Association NamePosition NameDuration
Suffolk County Matrimonial Bar AssociationPresident2014 - 2015
Suffolk County Matrimonial Bar AssociationVice President2013 - 2014

Legal Cases
Case NameOutcome
O'Loughlin v. Sweetland App Div 2nd Dept. 2009-02720Appellate Division Reversed

See all Legal Cases 

Publication NameTitleDate
Legal LeadersLegal Leaders: Long Island Top Rated Lawyers2014

School NameMajorDegreeGraduated
VillanovaLawJD - Juris Doctor1992
University of Notre DameFinanceBBA - Bachelor of Business Administration1987

Speaking Engagements
Conference NameTitleDate
Hot Button Topics in Matrimonial and Family Law - November 7, 2014Hague Convention and Other International Treaties and laws and effects on counseling clients2014
Matrimonial Boot CampFinancial Disclosure2010