Phillips broke a scoreless tie with his first goal in the 65th minute. He received Keammar Daley's pass, dribbled toward the left wing of the penalty area, eluded defender Jonathan Lopez and beat goalkeeper Ricard Jerez with a shot that landed inside the right post.
Jamaica (2-0-0) clinched the victory on Philips' second goal in the 78th minute. Dane Richards dribbled toward the end line of the Guatemalan penalty area and centered a pass to an unmarked Phillips near the 6-yard box. Phillips' shot eluded Jerez.
Guatemala (0-1-1) played the final 20 minutes a man down after Cristian Noriega's second yellow card infraction.
The victory assured Jamaica a berth in the Gold Cup quarterfinals. Jamaica leads the group with six points and Guatemala has 1 point.
Phillips' goals punctuated Jamaica's strong offensive showing in the second half. Jamaica nearly broke through with two scoring opportunities in the first 5 minutes after the break.
Luton Shelton dribbled from midfield into the Guatemela penalty area, where Jerez made a leg save of his 12-yard shot in the 47th minute. Jerez was tested again 3 minutes later when he stopped Richards' 20-yard shot
Guatemala had its best scoring opportunities late in the first half. Jamaica goalkeeper Donovan Ricketts stopped Carlos Ruiz's 20-yard shot in the 40th minute.
Ruiz found an opening in the 42nd minute but his shot from 25 yards out went about 4 feet wide of the right post.
The match's first 10 minutes consisted of repeated clashes but neither side was carded. Jamaican defender Dicoy Williams limped off the field with an injured right leg in the sixth minute and didn't return.
Honduras and Grenada play their second group match later Friday.
The third and final Group B matches will be played Monday in Harrison, N.J. Jamaica will face Honduras while Guatemala will play Grenada.