Bangladesh may have been blanked in a recent three-Test series in Sri Lanka, but have given a good account of themselves against higher-ranked sides in the shorter version of the game.
They made history at the World Cup in the Caribbean earlier this year when they qualified for the second round for the first time, beating Rahul Dravid's Indians in a group game.
Bangladesh also defeated then top-ranked South Africa in the second round, underlining how they are capable of surprising big teams on their day.
Vice-captain Mashrafe Mortaza said Bangladesh would seek inspiration from their recent big wins and be more competitive against the hosts in the one-dayers.
"As a team we are better in one-dayers than in Tests. You will see a different Bangladesh in the one-day series," the fast bowler said ahead of the three-match series.
The second and third one-dayers will be played here on July 23 and 25.
The tourists warmed up for the series with a three-wicket victory over a Sri Lanka XI in a practice match here on Wednesday, with middle-order batsman Aftab Ahmed scoring an unbeaten 92.
Sri Lanka will be without ace bowlers Muttiah Muralitharan and Chaminda Vaas, both on county duty in England.
Off-spinner Muralitharan was Bangladesh's chief tormentor in the Test series, finishing with 26 wickets to become only the second bowler to claim 700 Test victims after retired Australian leg-spinner Shane Warne.
Hard-hitting opener Sanath Jayasuriya, the only Sri Lankan to score 10,000 one-day runs, returns to the squad after missing the Test series.
The tourists have asked left-handed opener Shahriar Nafees to stay back for the one-dayers after leaving him out of the original 15-man squad.
Bangladesh have won just one of their 18 matches against Sri Lanka, the lone win coming at home last year.
Bangladesh (from): Mohammad Ashraful (capt), Mashrafe Mortaza, Aftab Ahmed, Tamim Iqbal, Shahriar Nafees, Javed Omar, Tushar Imran, Saqibul Hasan, Shahadat Hossain, Syed Rasel, Mohammad Rafique, Abdur Razzak, Farhad Reza, Mahmudullah Riad and Mushfiqur Rahim (wk).
Sri Lanka (from): Mahela Jayawardene (capt), Upul Chandana, Dilhara Fernando, Chamara Kapugedera, Farveez Maharoof, Jehan Mubarak, Chamara Silva, Malinga Bandara, Tillakratne Dilshan, Sanath Jayasuriya, Nuwan Kalusekara, Lasith Malinga, Kumar Sangakkara (wk) and Upul Tharanga.