Sri Lanka fast bowlers Ruchira Perera and Farveez Maharoof paved the way for a five-wicket victory in the opening one-day international on Monday by taking six wickets in Bangladesh's total of 118.
Kumar Sangakkara then hit 50 as the visitors reached their victory target in 24.1 overs.
Opening bowler Perera took three for 23 while Farveez Maharoof had three for 30 after the hosts decided to bat.
Bangladesh collapsed to 37 for five inside 11 overs after the Sri Lankan bowlers found raw movement at the Shaheed Chandu Stadium.
All rounder Khaled Mahmud, playing the last match of his career, offered resistance with 36 while Aftab Ahmed (21) and Alok Kapali (19 not out) were the only other batsmen to reach double digits in Bangladesh's 35.5-over innings.
For Sri Lanka, Sangakkara hit a six and seven boundaries while Mahela Jayawardene hit five fours in his 37 not out. Left arm spinner Mohammad Rafique took two Sri Lankan wickets for 10.
Bangladesh skipper Habibul Basher blamed his batsmen's lack of match practice for the disappointing result.
"It is failure of our batsmen who were away from international cricket for more than four months."
"They could not utilise a good wicket. But I hope to build up a fight and come back in the series," Basher told reporters.
Bangladesh innings (50 overs maximum)
Rajin Saleh lbw b Maharoof 7
Shahriar Nafees c Sangakkara b Maharoof 0
Aftab Ahmed b Perera 21
Mohammad Ashraful c Sangakkara b Maharoof 4
Habibul Bashar c Jayawardene b CRD Fernando 2
Khaled Mashud c Sangakkara b Perera 0
Khaled Mahmud lbw b Jayasuriya 36
Mohammad Rafique c Jayasuriya b CRD Fernando 6
Alok Kapali not out 19
Mashrafe Mortaza b Perera 6
Syed Rasel c Perera b Jayasuriya 7
Extras (w 7, nb 3) 10
Total (all out, 35.5 overs) 118
FoW: 1-5, 2-31, 3-35, 4-36, 5-37, 6-51, 7-82, 8-98, 9-109, 10-118.
Maharoof 8-1-30-3 (3w)
CRD Fernando 6-0-23-2 (1nb, 2w)
KHRK Fernando 5-0-23-0 (1nb, 1w)
Sri Lanka innings (target: 119 runs from 50 overs)
J Mubarak b Syed Rasel 4
ST Jayasuriya b Mashrafe Mortaza 13
KC Sangakkara c Mashrafe Mortaza b Alok Kapali 50
DPMD Jayawardene not out 37
CK Kapugedera c Alok Kapali b Mohammad Rafique 0
TM Dilshan b Mohammad Rafique 2
KHRK Fernando not out 0
Extras (lb 1, w 7, nb 5) 13
Total (5 wickets, 24.1 overs) 119
DNB: MF Maharoof, PDRL Perera, CM Bandara, CRD Fernando.
FoW: 1-11, 2-41, 3-111, 4-111, 5-117.
Mashrafe Mortaza 7-0-30-1 (3w)
Syed Rasel 7-0-35-1 (5nb, 2w)
Abdur Razzak 3-0-20-0
Khaled Mahmud 2-0-15-0 (1w)
Mohammad Rafique 3-1-10-2
Alok Kapali 2.1-0-8-1
Bangladesh full substitute: Abdur Razzak replaced Shahriar Nafees in the 13th over of Sri Lanka innings.
Sri Lanka full substitute: KS Lokuarachchi (unused).