Porterfield won the toss and elected to bat first and his decision looked to be justified as he and Paul Stirling got the innings off to an impressive start in Hamilton.
The duo managed to bring up the 50 partnership in the eighth over as both batsmen were able to find the boundary off the India seamers, who provided width in their early overs.
Ed Joyce arrived at the crease fresh off a century in his side's win over Zimbabwe, but he was out for just two as he was clean bowled by Suresh Raina.
However, Niall O'Brien and Porterfield kept the scoreboard moving and guided Ireland past the 100-run mark as the skipper notched his half-century off 65 balls.
The pair were solid at the crease as they were able to find the boundary with regularity while taking the runs that were on offer with the field back as they reached their 50 partnership.
O'Brien and Andy Balbirnie rebuilt the innings as the Leicestershire man maintained the intensity of his knock to smash three sixes over the rope to guide his team over 200.
O'Brien finally fell for 75 as he edged Mohammed Shami behind to Dhoni to leave Ireland desperately scraping for runs in the final overs.
John Mooney and Alex Cusack showed fight at the crease to add 21 for the final wicket to propel their side to 259 all out as Shami notched the wicket of Cusack with the final ball of the 49th over, his third wicket of the innings.