Fields was drafted by the Miami Dolphins in the seventh round (225th overall) of the 2007 NFL Draft. The pick used to select Fields was acquired from the St. Louis Rams earlier in the offseason in exchange for punter Donnie Jones. Fields was the first punter drafted by the Dolphins since Brent Bartholomew in 1999 and was the first rookie to handle punting duties for the team on a full-time basis since Reggie Roby in 1983. On May 24, the Dolphins signed Fields to a four-year contract.

Fields attended Michigan State University, and played for the Michigan State Spartans football team from 2003 to 2006. He earned numerous honors during his freshman season in 2003. He led the Big Ten Conference and was second in the nation with a 46.4-yard average. In a game against Nebraska, Fields set an Alamo Bowl record with a 62-yard punt.

Fields had the most productive season of his collegiate career as a sophomore in 2004, leading the nation with a 47.9-yard punting average. Honors on the season included numerous All-Big Ten and All-American selections. He was also a finalist for the Ray Guy Award, given annually to the nation’s top punter.

As a junior in 2005, Fields handled the kickoff duties for the first four games of the season in addition to being the team’s punter. He wrapped up his collegiate career with a 45.0-yard punting average as a senior.

During the 2008 offseason, it was reported that new Dolphins Vice President Bill Parcells “absolutely loves Brandon Fields.” The team did not pursue competition for him that offseason or since.

On December 13, 2010, the Big Ten Conference instituted the Eddleman-Fields Punter of the Year award to honor Fields and Thomas “Dike” Eddleman, Illinois punter from 1946 to 1948.

On December 27, 2013, the NFL announced Fields as a selection for the 2014 Pro Bowl.

Fields signed with the New Orleans Saints on October 6, 2015, to replace Thomas Morstead while he recovered from a strained quadriceps. Fields played in two games, and was then released on October 20, 2015.

In 2016, Fields earned a Master of Business Administration degree from the University of Miami Business School.

On September 29, 2017, Fields announced his retirement from the NFL.