The ICC released its latest rankings update on Wednesday, with Nasum climbing three places to eighth and Mahedi making an impressive 10-place jump to ninth.
Nasum now sits on 690 rating points, while Mahedi has 687 points, putting both Bangladesh bowlers among the leading T20I wicket-takers in the world.
The biggest movement at the top saw Afghanistan star Rashid Khan reclaim the No. 1 position after overtaking Pakistan’s Abrar Ahmed. Rashid moved to 720 rating points, while Abrar slipped to second with 718.
Abrar managed just one wicket in two matches at the Asian Games in Japan, while Rashid returned to the top despite not featuring in a match.
India spinner Axar Patel also made a major leap, climbing 16 places to seventh.
Elsewhere, Pakistan all-rounder Mohammad Nawaz dropped four places to 12th, while Salman Mirza fell seven spots to 23rd.
In the T20I batting rankings, India captain Shreyas Iyer broke into the top 10 for the first time, rising 18 places to seventh after scoring his maiden T20I century against the West Indies.