While Asian Games silver-medallist Manpreet clinched a comprehensive victory over Seychelles' Keddy Agnes, sixth seed and Commonwealth Games champion Manoj got the better of 2011 European champion Fatih Keles of Turkey.
Both Manoj and Manpreet had got first-round byes. Manpreet won 3-0 in the overall analysis with the round-by-round break-up being 30-27 30-27 30-27.
Manoj, on the other hand, fought through a see-saw battle even though he too emerged 3-0 victorious at the end of the bout.
The 28-year-old Manpreet will now face world number one and Olympic bronze-medallist Teymur Mammadov of Azerbaijan, who has been top-seeded, in the round of 16 on Monday.
Manoj, meanwhile, will be taking on Canada's Yves Ulysse, who defeated Juan Romero of Mexico. The Manoj-Ulysse clash is also scheduled for Monday.
"Manoj fought from long range in the opening round and in the second round, the other guy resorted to some tempo boxing. It was an intense bout but Manoj dominated the final round," said Sandhu.