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  The home side finished on 151-7 in reply to Glamorgan's 176-5, despite Michael Klinger's 52 off 34 balls.
  Miller struck his 50 off 33 including three sixes, as the Welsh County moved to the top of the south group table.
  Rudolph's 51 off 46 was a more measured effort, while Sri Lankan seamer Thisara Perera bowled tightly for his 2-25.
  Glamorgan moved ahead of Surrey on net run-rate at the top as Miller showed his international class despite a patchy wicket which benefitted the medium-pacers.
  Klinger threatened for a while to get Gloucestershire in the chase in front of a packed home crowd, but Colin Ingram took 1-18 in a mean four overs while Graham Wagg claimed his 100th T20 wicket and the home side fell short.
  Man of the match David Miller told BBC Wales Sport:
  "I'm very happy to be one (win) from one, and looking forward to the next four games. I was a bit nervous for a couple of balls, it took me six or seven to get going but it's nice batting with Jacques Rudolph who has a lot of experience.
  "It's always good to hit the pavilion, the one I got out I was trying to hit over the top of the apartments, but it's nice to hit a few sixes and get the run-rate up.
  "Every single game I get nervous, but it's what you do with the nerves and where you take it - it's a short stint to make an impression but I'm just trying to play my game and enjoy it, which has been really easy with this changing-room."
target: Fifties for Glamorgan debutant David Miller and captain Jacques Rudolph proved key as they beat Gloucestershire by 25 runs in Bristol.