Bangladesh have carried the momentum from their landmark Test victory over Sri Lanka into the one-day international series, centurion Tamim Iqbal, together with Shakib Al Hasan, helping the tourists to record a 90-run win in Dambulla on Saturday.
Opener Tamim and all-rounder Shakib shared a dominant stand of 144 runs for the fourth wicket, as the Tigers posted 324-5, the fourth-highest ODI total by a visiting team against Sri Lanka and the first time Bangladesh have passed 300 in a 50-over game away to a top-tier nation.
The hosts wilted under the pressure of attempting to chase down that challenging target and were all out for 234 in the 46th over.
Dinesh Chandimal (59) and Thisara Perera (55) offered their only meaningful resistance, the result leaving Sri Lanka 1-0 down and needing to prevent another defeat in the second ODI at the same venue on Tuesday if they are to avoid losing the series.
Bangladesh's star man Iqbal (127) came close to carrying his bat as he found the boundary 15 times and supplied one maximum off 142 deliveries, the opener surviving until the 48th over before finally departing when he was caught at long-on by Danushka Gunathilaka off a short ball from Lahiru Kumara (1-74).
Sabbir Rahman (54) had offered the top-scorer good support with a near run-a-ball half-century before Upul Tharanga intervened to take a brilliant catch from a drive for Asela Gunaratne's only wicket.
Shakib fared even better, also rattling along to notch 72 from 71 balls, eventually finding Lakshan Sandakan at short fine leg as Suranga Lakmal (2-45) slipped in a slower delivery.
Mosaddek Hossain also weighed in with a useful 24, finishing unbeaten alongside Mahmudullah (13 not out).
After compiling a half-century to give the struggling hosts some hope, Chandimal was out in the 29th over trying to sweep Mehedi Hasan (2-43) and top-edging to Soumya Sarkar at short fine leg.
Gunaratne (24) and Milinda Siriwardana (22) followed skipper and opener Tharanga (19) in getting out cheaply after starts, while two key men - opener Gunathilaka (0) and Kusal Mendis (4) - failed altogether, rendering the late resistance of Sachith Pathirana (31) and Perera futile.