Jess Phillips graduated from Charlton Pollard High School and played at the position of safety for Michigan State University. He played in the historic 10-10 tie between undefeated Michigan State U. and undefeated Notre Dame. 

During his senior season, he forged a check and was sentenced to 18 months at the penitentiary at Jackson, Michigan. He was paroled after four months; he credits his time in prison with teaching him a lot about life, but he gave up hope of being drafted into pro football.

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But the expansion Cincinnati Bengals and coach Paul Brown were willing to take a chance on Phillips. He was drafted as a defensive back in the fourth round (84th overall) of the 1968 NFL/AFL Draft by the then-AFL Bengals. He was released from prison on August 2, 1968, and was met by Paul Brown's son, Mike Brown, who took Phillips directly to the Bengals training camp in Wilmington, Ohio, where he was installed as a defensive back. Paul Brown called Phillips "a kid with an engaging personality who has it all in front of him."

In his rookie season (1968) and the expansion Bengals' first season, he played strong safety. In 1969 he was switched to fullback and came on strong with 118 carries for 578 yards (a 4.9 average) and three touchdowns, including a career-long 83-yard run. He also caught 13 passes for 128 yards, a 9.8 average.

In his third season, he started all 14 games and increased his totals to 163 carried for 648 yards (a 4.0 average) and four touchdowns, plus 31 receptions for 124 yards and one touchdown. In 1971, he started 10 of 14 games, with 94 carries for 420 yards (a 4.5 average) and 22 receptions for 125 yards and one touchdown.

Phillips joined the New Orleans Saints for the 1973 season and thrived as a starter for all 14 games. He totaled 198 carries for 663 yards (both career highs), although his yards-per-carry average fell to 3.3. He also had 22 receptions for a career-high 169 yards.

In 1974, he was no longer a starter but still played in all 14 games with 174 carries for 556 yards (a 3.2 average) and two touchdowns with 11 receptions for 55 yards.

By 1975 he joined the Oakland Raiders, for whom he played in all 14 games, starting two, and had 63 carries for 298 yards (a 4.7 average) and one touchdown with four receptions for 25 yards. He also returned 12 kicks for 310 yards, a 25.8 average.
In 1976, he was a member of the New England Patriots, for whom he played 13 games with 24 carries for 164 yards and one touchdown with one reception for 18 yards. He also returned 14 kicks for 397 yards, a career-high 28.4 average. His last season was 1977 with the Patriots. He played all 14 games but with only five carries for 27 yards and one touchdown.