Hillard, who spent eight seasons with the New York Giants and four with the Tampa Bay Buccaneers before retiring due to a neck injury after the 2008 season, spent the previous two seasons coaching with the United Football League's Florida Tuskers. He was their wide receivers coach last fall.
The Palm Beach Post reported later Tuesday that receivers coach Karl Dorrell was moved from receivers coach to quarterbacks coach.
Dorrell will replace David Lee, who left to become the offensive coordinator at Mississiippi after three years with the Dolphins.
Dorrell is among the holdovers from coach Tony Sparano's staff following a horrendous offensive campaign. Only the Cleveland Browns and Carolina Panthers scored fewer points than the Dolphins did this past season.
The Dolphins in the last week hired Brian Daboll to be offensive coordinator, brought in Jeff Nixon as running backs coach and Darren Krein as strength and conditioning coach, and promoted Dan Campbell to be tight ends coach.
The Herald reported, citing sources in Mobile, Ala., for Saturday's Under Armour Senior Bowl, that there will be "considerable changes" to several assistants' assignments.