The evergreen striker, who signed a one-year deal at Bloomfield Road following his release from Birmingham, struck again three minutes after the restart with another predatory effort.
The visitors pulled a goal back through George Boyd in the 82nd minute but Blackpool hung on for victory.
Holloway named the same starting line-up that won at Hull, but Peterborough arrived on the Lancashire coast in buoyant mood after beating Crystal Palace in their opening game.
It was the hosts who began the brighter and they almost led inside the sixth minute following an outswinging corner by Elliot Grandin.
The ball reached Phillips at the far post and the veteran frontman planted a close-range header goalwards.
Posh goalkeeper Paul Jones made a fine stop to avert the danger and Grandin followed up to strike the ball against a post from distance.
The Seasiders continued to build up a head of steam and in the ninth minute defender Alex Baptiste advanced forward before striking a left-footed shot wide from 12 yards.
The visitors survived the early storm and steadied themselves before fashioning their first goalscoring opportunity in the 11th minute.
Lee Frecklington hit a right-footed shot from 25 yards but his effort was diverted out for a corner by Blackpool midfielder Keith Southern.
Grant McCann delivered the resulting corner from the right flank and Ryan Bennett's six-yard header was parried to safety by Blackpool goalkeeper Matt Gilks.
Midway through the first half Blackpool went close when a cross from Gary Taylor-Fletcher was met by Phillips but his header was well parried by Jones.
However, the hosts finally made the breakthrough in the 44th minute when Baptiste crossed from the right flank and Phillips headed into the top corner from 12 yards out.
And he underlined his eye for goal again three minutes after the restart as another fine finish put Blackpool 2-0 up.
Southern's fierce strike from 18 yards was only parried by Jones and Phillips followed up to sweep home the rebound from close range.
David Ball then sought to get Peterborough back into the game but his shot from distance was well saved by Gilks.
Blackpool almost grabbed a third in the 58th minute when Baptiste crossed to Brett Ormerod who could only fire wide from just six yards out.
Posh boss Darren Ferguson then made three substitutions in quick succession in the final quarter of the game.
The changes breathed new life into the visitors as Boyd struck with a right-foot shot from six yards with eight minutes remaining after a mistake from Cathcart - but Blackpool held on.
