The win in Wellington on Saturday gives the home side a 1-0 lead in the three-match series.
Earlier, Matt Henry took 4-19 as New Zealand bowled Sri Lanka out for 178 in just over 43 overs in a match played in chilly conditions at the Basin Reserve.
New Zealand was 1-180 when they reached the winning target in the 27th over.
Young posted his 11th ODI half-century and Ravindra returned to form with a bright 45 from 36 balls which included six fours and a six. Mark Chapman was 29 not out at the end.
"Obviously, changing formats and getting back into some one-day cricket, the guys were excited," said Henry.
"It was great to get the series underway."
New Zealand won the toss and sent Sri Lanka in on a pitch that had been covered because of recent rain, suiting the home team's four-pronged pace attack.
Avishka Fernando scored a gritty half century in an 87-run partnership with Janith Liyanage which provided the substance of Sri Lanka's innings, rallying the tourists after they had slumped to 4-23 in the 10th over.
Fernando made 56, his fifth ODI half-century, and Liyanage 36, coming back into the team after missing the three-match Twenty20 series which New Zealand won 2-1.
Henry, Nathan Smith and Jacob Duffy all claimed early wickets to put Sri Lanka on the back foot, then New Zealand captain Mitchell Santner broke the key partnership between Fernando and Liyanage.
The teams meet again at Seddon Park in Hamilton on Wednesday.
27°C