The International Association of Chiefs of Police meets through Tuesday.
Holder is scheduled to speak on Monday, along with FBI Director James Comey.
A day later, Boston Police Chief Edward Davis is set to discuss the Boston Marathon bombing.
The conference will also feature a session on the Sandy Hook school shooting in Newtown, Conn., along with panels on officer-involved shootings and cyber attacks.
Philadelphia Police Chief Charles Ramsey opens the event with remarks Saturday.
The gathering is being held at the Pennsylvania Convention Center.