The index closed 17.85 points lower after falling 1.66 points on Friday.
Trading on the Ho Chi Minh Stock Exchange (HoSE), on which the index is based, surged 22% to VND32.13 trillion ($1.34 billion).
The VN30 basket, comprising the 30 largest capped stocks, saw 26 tickers in the red.
GVR of Vietnam Rubber Group plunged 4.2%, followed by SHB of Saigon Hanoi Commercial Bank with a 3.1% decline.
VRE of retail real estate arm Vincom Retail dropped 3% and STB of Ho Chi Minh City-based lender Sacombank closed 2.8% lower.
Three blue chips bucked the trend. SAB of brewer Sabeco went up 4.3%, PLX of fuel distributor Petrolimex 1.1%, and VPB of private lender VPBank 0.5%.
The HNX-Index for stocks on the Hanoi Stock Exchange, home to mid and small caps, dropped 1.90% while the UPCoM-Index for the Unlisted Public Companies Market fell 1.07%.