IAP2 is an international association of members who seek to promote and improve the practice of public participation in relation to individuals, governments, institutions, and other entities that affect the public interest in nations throughout the world. IAP2 carries out its mission by organizing and conducting activities to:

• Serve the learning needs of members through events, publications, and communication technology;
• Advocate for public participation throughout the world;
• Promote a results-oriented research agenda and use research to support educational and advocacy goals;
• Provide technical assistance to improve public participation.

IAP2 was founded in 1990 as the International Association of Public Participation Practitioners (IAP3) to respond to the rising global interest in public participation. The initial mission was to promote the values and best practices associated with involving the public in government and industry decisions which affect their lives. The founding members assembled a Board of Directors, developed by-laws and policies, and organized the first annual conference in Portland, Oregon, in 1992. Practitioners, both professional and volunteer, were identified as the primary constituents for membership; a newsletter and an annual conference were selected as initial IAP2 activities.

IAP2 quickly grew and developed into an organization which looks beyond the formal practitioner to include all people involved in public participation. IAP2 added a semi-annual journal, website, and local chapters to its list of services. In 1996, IAP2 changed its name to reflect this growing diversity and inclusiveness of membership. The organization has grown from 300 members in 1992 to more than 12,500 in 2019, with members from 26 countries. IAP2 regions were formed beginning in 2010 to better meet local needs. 

In the past few years, IAP2 has continued its growth and established itself as a leader in the field. In 1999, IAP2 launched its Certificate Training Course in Public Participation providing comprehensive training in the tools and skills needed for effective participation and the Emotion, Outrage in Public Participation course in 2009. The Certificate course was updated in 2015 and renamed to Foundations in Public Participation. Also in 2015 IAP2 Canada and IAP2 USA launched professional certification programs open to all IAP2 members worldwide. Conferences have been held in North America every year since 1992, alternating between IAP2 USA and IAP2 Canada regions.